if the key doesn't have a chip it in or anything then you can go anywhere that keys are made, so basically if its just a regular key, i wouldn't go to wal-mart because i've heard some of their keys don't work but i'd go to Lowe's Home Improvement, i got a key made there for my 98 chevy silverado and it works like a brand new key, if they mess up they'll make another key for no extra charge and if they can't get a key to work right you'll get your money back
now if it does have a chip in it (which i highly doubt for a 93) then you'd have to go to the dealer