Foam is one of those useful things to stash, as it come up in your life - packing foam, pickup-height foam, guitar case-fitting foam.... along with varying thickness of shim plastic & wood screws & tubing, my foam collection is my pride & joy! :hello2: I try to keep a package of this stuff around:
http://service.maddak.com/catalog/766900183.asp
The tan stuff is 1" diameter, you can cut down sections to put into pickup cavities, wrap towels around it to make pads to make a guitar fit tightly in a case, beat on yer cat with it.... unlike cheap foam it's not gonna decompose inside your guitar in a year. Any drug store that carry canes and pads and stuff for handicapped people can order it.