I'm almost done building my proton pack but a need a little help. What should I use for the tip of the gun (the white thing), preferably something easily found.

Norm suggests “Feed Through Wall Tube” at Radio Shack. The guys at ASAP have a better way Click Here

i would use a candy clear tube like the one with runts in it and ussally has a pumpkin or something on top of it.

If you have a shop with those coin collector folder booklets in it, and a bunch of coin collecting books, ect. you can find little clear plastic coin tubes. They're stronger than the ones with candy in ‘em, and they come in 3 or 4 different sizes to choose from. you can find em in a lot of book stores, and hobbyshops, I’ve even seen them in walmart.