Some of these are pretty hard to find. The DIC stuff may be out there but in my experience it usually shows up in the drawers of former dealers and seldom as a complete lot. Recently, there was a complete vertical DIC set, that came out of a storage container.
The # 1242 condenser, used for phase is perfectly usable as a dry ,high N.A. BF condenser. It's a pretty sophisticated condenser . Although no data shows up for it. It's .90 or .95. If you want an abbe or abbe aspheric oil 1.25 condenser that you can thread into that condenser body, I have one.
It would be a labour of love to replace the mirrors in that trinocular. Could be done. Trinoculars are available but I guess their internal integrity would need to be verified by the seller.
Aperture viewer? I guess you mean the bertrand lens version with the flip in flip out prism? I have one of those too.
Polarizing equipment is hard to find. It is out there but usually still attached to systems. Occasionally you see an individual strain free objective or condenser, so I would be inclined to keep looking and pick up what you can, when you can. There are some after market rotaing polarizers to fit over the illuminator window.
Phase objectives , show up on occasion. Same protocol as for the pol stuff.
There are only 4 higher N.A. objectives that fit the bill of your description.
1) cat.# 1303 63X .80 SPL achromat. This was designed at Reichert Austria for their 34mm parfocal microscopes which mostly used AO objectives redesigned with spring noses and different barrels. The design was reviewed and approved by AO for inclusion into their objective lineup in Sept. 1982. Not a whole lot of them were sold. Occasionally, you see one in North America but there are more of them in Europe. Unfortunately, sometimes at very high prices. The European version and the North American version are identical, even inclusive of the spring loaded nose.
https://www.ebay.at/itm/Reichert-Jung-M ... Swr~lYrKJg
2) cat.# 1016 50X .80 oil immersion planachro w./ iris. A nicely compatible objective with the 100X 1.25 oil immersion iris equipped # 1014. For DF they work as a nice team, since it always nice to be able to back out of a 100X oil objective to another oil objective, in order to get a wider view.
3) cat.# 1026 50X .85 oil immersion achromat w./iris. An older version of the above. I actually prefer it.
4) cat.# 1029 . This cat. # shows up very briefly in the mid to late 60's, as the first such objective offered for the new infinity corrected lineup. It seems identical to the above , minus the iris and the cat.# later shows up as a 100X 1.25 N.A. oil planachro, after the 50X was discontinued and replaced by the 1026. I have never seen one.
5) Additionally, they made two 40X apos and a 40X .85 achromat. These have the resolution to carry 15X cat.# 184 eyepieces with grace and yield 600X magnification , dry. The original apochromat was a 40X .85 with a correction collar. It had no cat.# that I can find and is very rare. Physically, it looks like the last incarnation of the 160mm 43X .95 apochromat with the brushed chrome barrel but it is clearly marked infinity. It's production was short lived. In the 80's they released the cat.# 1809 40X .85 advanced achromat. Also uncommon. The most common was the # 1323 40X .80 planapo without a correction collar.
DF condensers for the series 10/20 are quite common. There is almost always one on ebay for sale. The common one is the 214F but there were actually 3 types. The 218F is self illuminated and the K2172 is toric, so works down to 10X . All are excellent cardioid oil condensers. You will need either a #1079 100X 1.25 achromat fitted with a funnel stop, a # 1027 100X 1.25 achromat w./iris or a #1014 100X 1.25 w./iris. to get high resolution DF with any of them .
https://www.ebay.com/itm/AO-Series-10-D ... SwCahc3Kyj
As far as compatible equipment from other manufacturers, that would be a complete accident and discoverable only by chance outside of the AO-Reichert-Leica family of microscopes. The Reichert-Leica branch fed off of the AO introduction of infinity, so there was a line of Reichert Austria microscopes that used AO optics. One such , is the Neovar 2. I don't think they were marketed in North America but the optics and accessories would be compatible with a series 20, if in the case of the accesories they physically fit. The objectives are the same but spring loaded. The only other option is to change the head to a series 400 head. Then, any Reichert branded D.I.N. optics would work( lowering the stage makes the substage area pretty tight), as well as early Leica Delta optics and some HCX with adapters. Accessories could work too but may need adapters. Olympus oo objectives would also work with a 10% change in magnification and some Chinese D.I.N. oo, with the same proviso.