So where could I buy the plastic weather stuff that goes in between my door panel and door I'd like it precut and what not

 

The clear plastic sheet?

 

I doubt you are going to find it anywhere...... I would think either the dealer, or, maybe LMC truck, but, don't hold your breath. I usually cut/remove as necessary, and then duct-tape it back together. Or, just leave it off entirely.

 

You can use a sound deadening sheet, Works better than plastic to keep out noise. Most of them are asphalt based so water wont leak through.