You know, given how easy it is to seal a seam, I think it might be possible to extend a pad, assuming could remove some from a matching pad. So, it sounds like you should get together with someone cutting down their pad and have them send you their cut-off. I don't need to extra length myself but I am now tempted to try this out since I have the materials here.
What specific pad are you using? What pad would you like to use if it was long enough?