Auto Transmission Problem- need parts.

Hey there everyone, my name is Bobby and I'm brand new to this fourm.

Ive got a 2004 tib, tidal wave and I love it.

Its got the 2.0L engine with a 4-speed auto with sport-shifter.

I got in a pretty bad wreck back in november and I've been slowly making repairs to get her back up to par. One of the last things is my transmission keeps defaulting into 3rd, I've decided it's the low reverse solenoid in the transmission. does anybody here know where I could buy specific parts like that? They dont have them at my local auto parts store.

Thanks.