I have the 92 Sidekick 2D 4WD 1.6L 6-speed manual that lost 2 forward gears (don't ask how!). I purchased a used transmission from Automatix.com online. It came in surprisingly good and clean shape. I was told it was the same transmission for 1992-1998 Sidekicks, at least for the 4WD manual (didn't ask about A/T or 2WD). I ended up with a 1998 transmission, which went in with no problems and working well. When I ordered it, they were very careful to check my VIN number for compatibility. I'm sure all reputable online dealers do the same. If they don't ask for your VIN - be very wary about what you'll get. Also, most online providers will drop ship to the garage of your choice if you don't do the work yourself. So shop around, call when you see a good price (low $500 or less) and availability, and confirm compatibility with your VIN.
Good luck, and let us know how it goes.
Your baby Sidekick just runs so much nicer with a working transmission! :-)