you could write to the company who made your trousers claiming to be a student doing some research at college and ask for a free sample - a mate of mine did that and they sent him enough to make a pair of trousers!
Removed User26 Apr 2006
In reply to Huddy: hey good plan thanks i might try that
In reply to Removed User:
the patches I used were useless this winter they delaminated after only a few uses. Luckily underneath I also used seam seal, which is far better IMHO