The spring that I have out of the rear of the transmission measures 2 3/4" (70 mm) long by 1 1/8" (30mm) wide (OD). The spring wire is about 2 mm.
It's probably not an item where you need to spend a lot of time trying to find a substitute for. I would think someone would have one they would be willing to part with for a minimal amount. But, if you find a substitute somewhere, post it.
Trey, I do have a spring and you can have it. Unfortunately I can't get it out of the transmission. It came out part way but won't go any further. I have twisted and pulled to the point where it's going to damage the spring if I try any harder. So, here is the deal. Come get it and you can have the whole transmission. It's perfect, it's the one that came out of my car. and I'll also throw in another one that I "think" is good, but I honestly don't know anything about it.