I went to lowe's today and told the guy in the paint dept what I wanted to do, he gave me some Durham's Rock Hard water putty. I'll try it out tonight and post pics and a review next week.
I Have a plastic Darth Vader head that came with candy in it. Filling it with the putty and then will drill and tap it. Also have an R2D2 that I can change out or use on the transfer case.
I like that transformers knob, that came out good.