Pin Ball Resource is THE place for licensed Gottlieb parts, and has lots of pinball parts for all brands of machines. This is an old fashioned business - phone calls work best, and the website is not totally up to date. If you need a hard to find part, Steve likely has it.
If you have time, search the threads for Pinball Resource or PBR or specifically, Steve at Pinball Resource. He is a wealth of information, but is very direct. If you don't have the part number, do some searching first. If you have the wrong part that doesn't go for your machine, he will let you know.