I couldn't really find anything on Radio Shack, but I did find this link in the Props section of ghostbusters.net. Here's the link http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=AEC&type=store
There is a guy that sells a LED set-up that is for Proton Packs. He has them ready to install into your pack, it includes the Blue Lightbar and the Cyclotron… http://www.hyperdynelabs.com/gb.htm
You can also buy a sound kit from him too… but it's really exspensive. I'm working on my own for around $40… but that won't be for a while.