John Goodman is very good to deal with and I've used a few of his kits in the past. But sometimes when you need a light seal kit you need it right now, so a few years ago I started cutting my own seals from sheets. You can usually get an assorted pack of sheets from eBay that have foam and neoprene in various thicknesses, and companies like Polar Bear Camera (
https://polarbearcamera.com/) sell a big variety in larger sheets. You'll need a cutting matt, steel rule, and a scalpel to accurately cut your own strips, but given the amount of material you have in front of you one slip up won't stop the job.