Hello fellow FX16 owner
Yes, there are only 2 belts. AC and PS sharing one of them.
The tensioner is nothing more than a bolt with a pully assembly at the end. I'm on my 3 "tensioner" pully. I pulled my last one from a AE92 GTS. Try to expand your search to anything front wheel drive 4AGE powered if you have no luck finding FXs. I've actually run into several FX16s at my PnP, so don't rule out PnP for future parts.
I'd just try a belt, pulley, and some ps fluid to see if it works. Don't invest in a pump when you may not need it.