Where can I source the rivets needed to attach the plastic trim clips for race track trim and the back window belt trim. Thanks for any help

 

Just use a standard 1/8th inch aluminum rivet. There're cheap and do the same thing. All my trim is attached with then and no problems.

 

Thank you for your help

 

The originals were studs welded to the body. You can use a gun like this to weld them on with the correct attachment. Stud Gun Welder Auto Body Repair Tools Dent Ding Puller Kit w 2 lb Slide Hammer | eBay
I did my truck this way, I didn't want to drill a bunch of holes in the body. Every hole you drill is an invitation for rust to start, especially if you use dissimilar metals like aluminum rivets in a steel body.

 

Eastwood has the special rivets for the moulding clips, but like others have said, you need the stud gun to attach them.
Stud Welder Trim Rivets bag/500