I don't know if this was the exact amscope head I started out on, but it looks very similar.
I was able to hook my canon rebel up to it with an eyepiece adapter, which worked but had a few issues with hotspots. That probably will be the same with any camera though. You might want to consider a dslr for the camera--a good used canon t6 is 18mp, has good live view and remote shooting with their freely availably eos utility, and should cost around 200 dollars. They are certainly bulkier and adapting one may be more expensive. Still, I think the end result is worth it. I had I think a 5mp amscope camera on my amscope head, and I wasn't very happy with its performance. It also seemed to be interpolating to fake the last bit of resolution, though that may have been a wrong setting or something.
I'd note about the similar amscope I had, overall its performance as a scope was OK, definitely not garbage but not breathtaking either. Of course it's at an attractive price point (especially for a trinocular head), so if you decide to upgrade later you won't be out as much. Don't expect much resale value, just as a heads up. I ended up almost giving mine away, including the basic gemological base it was on.
As a general, obligatory note, you might want to consider a used high-end scope instead of a new medium-end one. I didn't get really excited about stereo microscopy until I upgraded from my similar amscope to a b&l stereozoom 7. I have also found used microscope sales are kind of slow right now, and because of that you might have some luck making offers in your price range on higher-priced used equipment. As an example, here is a stereozoom 7 trinocular scope that comes with a boom stand and a fiber optic illuminator, listed as good condition (so if it comes and is not functional you can return it at their expense). Here is another. And here is a third.
All three have high asks, but I suspect at least one might take a low enough offer to fit within your budget. A trinocular SZ7 will need a bit of extra adapting work, but I just put up a thread with instructions on how to adapt a dslr to it, which costs about 100 dollars. If you were to make an offer that kept within your budget you could end up way ahead.
Even if you're stuck on buying amscope, here's a used one (perhaps the same model?) for 270. https://www.ebay.com/itm/AmScope-7X-45X ... 3671821480