Yeah, good & properly sized 15" tires are hard or impossible to come by.
I ran my car a few times on a 15x7/15x9 combo. 225/45-15 all around. Pinched on the 7 quite a bit, stretched on the 9. Tires are BFGoodrich Rival S (awesome 200tw tire!)
At 23" tall they're 2" shorter than what our cars should be using, which is pretty significant. Driving around on the freeway is irritating, many rpms to keep up with traffic.
In a perfect world you would want something like a 245/50 or 255/50-15 which
afaik doesn't exist at all out back, and with unmodified fenders to be safe something like a 205/60-15 up front. Those exist, but in no tire you'd actually want.
You didn't specify, but if you're just going for the hellaflush look and not the benefit of more rubber, you could always just spacer out your existing wheels. You may have to swap out longer studs to do it safely, but it can be done pretty easily. Another option.
Took me an afternoon to pull the hubs, swap studs, reassemble and bleed the brakes, and I'm a slow worker.