geo tranny trouble

I have a 96 geo tracker what trannys can I put in it it is an auto 3 speed now I want to just find another used and put it in it is a 2wd 2door convert
been trouble since I got it said the torque converter lock was bad and egr problem fixed everything I thought was wrong and had to put in a radiator and waterpump and timing belt and all too now the tranny slipping I just want to fix it good enough to get rid of it loking to buy a real suv a s10 blazer 4wd 4.3 auto by the way it is for the other half so imagine what I been through with this thing any help would be appriciated