True story. My aunt & uncle moved to a small town in Wisconsin. Every place was “the Smith place” or “the Jones place” or whatever, where Smith / Jones / etc. were the people that had lived there like 100 years ago.
They moved to town, and built a house. This confused everybody.
“Where do you live?”
My aunt & uncle would give an address.
“No, but who lived there before you?”
“Nobody.”
[stunned silence]
Mess dutifully ignored. If that’s the existing chair, it looks like a pretty standard off-the-shelf office chair. So if you’re happy with everything but the seat / back / etc., you might find that you could get a standard ergo office chair, just build the top part, and toss it on your existing base. That way you wouldn’t even have to mess with custom pistons or anything. Save the rest of the parts for swapping out later if necessary.
I personally have this:
I waited until it went on a good sale and managed to nab it for a little less than $200, and I threw on the SquareTrade protection plan in case anything went wonky with cushion / padding / etc. in the first couple years.
It works well for me, and you can build it with or without the arms depending on your preference.
No, it’s not as good as the fancy Aeron stuff - but it meets my needs just fine. It’s Office Depot / Max’s line of chairs intended for people who actually sit all day, and a year after I got it it’s still doing pretty good. You mentioned that you have an Office Max at least somewhere in your vicinity, so even if you had to order online you could probably return in-store if there was an issue. Although I’d definitely suggest seeing if they have any of them in stock and seeing how they feel, seat-wise.
I also swapped out the coasters, just to help it roll a bit better on my floors. I got these:
https://www.amazon.com/gp/product/B08CSGXTLD/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
They add a tiny bit of height (an inch-ish), but they help it roll much nicer.
Just some thoughts. 
