I've custom made some before. You usually have something laying around that you can use along with some anti static bags. Here are two good methods:
1) Draw a square and Dig out a small square portion of a styrofoam block and line it with anti-static bag.
2) cut out a few pieces of a cardboard box that's slightly larger than your processor. In the middle of each of those pieces, draw a square that's the same size as your processor and cut that out. Glue the peices together then line the inside with a anti-static bag.
Either of these methods work well. My gf always thinks I'm doing some arts and crafts each time I send out something that requires custom packaging.
