Do a search on eBay for seller ID "interslice" (Jon Goodman). Get the $6.00 kit, which he ships free within the USA. High quality materials, a "Camera Seal Repair for Dummies" instruction sheet (okay - he doesn't call it that, but you get the idea), and a "tool" for removing the old seals. Has enough material for several cameras.
Alternatively, email him directly at: jgood21967ATaolDOTcom
Another vote for Jon Goodman. Although I've never used his stuff, his name is mentioned with high praise on many a forum when the subject of light seals is mentioned.
Anyone who's used Jon Goodman's kits, are they modular or do you order for specific cameras? I've got some aging film backs that could use some new seals, and this seems like the one repair I could probably trust myself to to do.
They are generic (not specific to a single camera) with LOTS of material of different thicknesses and densities. If you do a search for his auctions they have a photo of all the materials in the kits.