The good news is that there are literally a ton of prospective candidates; the bad news is there are literally a ton of prospective candidates
if that makes sense? Also, what's the primary purpose (your preference for single stack sounds as though CCW).
That said here are some choices that I can personally attest to (now with the current hysteria supply may be spotty but they should be back-orderable at the very least):
1) Ruger P95 (new SR series shoot well when I rented it to try it out and is a bit more expensive but also great guns)
2) S&W Sigma 9mm
3) Taurus PT-92 or 24/7
5) Arcus 98 (great little Browning-like clone but it's DA not like the SA 94)
6) Kel-Tec P11 (very hi-cap compact 9mm)--PF9 is the single stack model.
As I said, there are lots out there and I just named a few.
*I know it about 15% more than your budget but if you can swing a Glock you can't go wrong (26 is a great little compact that will accept all Glock mags).