Pictures/links help lots... >>;
But you can find a white studded belt pretty much anywhere, they're not too uncommon. Try a Stitches or a CD store- the ones where I live have recently started stocking belts, which are mostly studded. You could also try a Claire's/Ardiene's. If all else fails, I'm sure you could scrounge one up on ebay or something.
Yoko's gun can be made with relative ease from a wooden broomstick, cerealbox cardboard, cardboard tubes, hot glue and paint.
That's how we made ours anyway. =P
And at the moment, I can't find a good ref. picture from post-timpskip Simon to look. =\
Edward Elric - 65%
The Medicine Seller - 10%