I got into repairing my own kites a couple of years ago.
You can buy it here but difficult to get small spools so it will be expensive.
Buy at some motor car trimmers and upholsterers and of course sail lofts if they are willing to help.
I got mine from US, quite cheap but mail is expensive:
www.sailrite.com/If you intend to do all your own repairs then best to buy both Black & White spool. 1 oz or 4 oz (about $5 or $15)
V92 Dabond Polyester for LE / HD repairs
V69 Dabond Polyester for sail cloth repairs
I also got some HD (about 5 oz ) Dacron cloth for repairing LE and reinforced panels.