Finding a 4-speed tranny would be quite a search that may not be worth your time, effort, or money.
You would fare better with a T50 5-speed tranny from the 77-87 RWD Corolla models. Note that the later versions found on the AE86 Corolla GT-S models have slightly better gear ratios than the older models, but they are harder to find than the earlier versions.
Try Car-Part.com:
http://www.car-part.com
Good luck,
__________________
Regards,
Nobody can break it better than me. 
88 I4 Slushie, 89 I4 5Sp, 89 V6 5Sp, 82 Corolla, 72 510, 88 Minitruck.