Filter access is a big reason for it. For those of us running header instead of exhaust manifold, changing the filter ends in oil on the pipes that you can't clean out completely.......the smoke is awful.
Try Performance Auto Transmission Center
A500/500/42RE/44RE/42RH/44RH Archives
They might have the solenoid plug. The neutral safety switch connector should be available on Rockauto still.
Salvage yards have them for a decent price, usually. The aftermarket ones are hit or miss for quality. You can search the part number online, and find a factory one from a dealer that sells at a discount.