It's not absolutely necessary to run an oil cooler but its greatly recommended to do so especially if you're running FI. Everyday driving shouldn't be an issue without one depending on where you live but if you plan on seeing any kind of track time you definitely wanna look into it.
Here's a few oil cooling solutions as well as a link for FT86speedfactory which sells some oil coolers as well. Perrin's oil cooler has seen some pretty good reviews based on others thorough the forum and ft86speedfactory generally has them in stock also.
Robispec
http://www.ft86club.com/forums/showthread.php?t=39819
FA20Club
http://www.ft86club.com/forums/showthread.php?t=52219
FT86speedfactory
http://ft86speedfactory.com/cooling-...2296c15abdd401