Hi there,
Have been looking for exactly the same thing. Came across these Sew In Trouser Pocket on the internet. Haven't bought it yet but it looks just up your street.
http://www.ribboncircus.com/index.php?cat=Repairs
Also if wanted to iron on repairs...
http://www.uksewing.com/p763/Sew'N'Care-Iron-on-Trouser-Pocket-Repair-Kit/product_info.html?osCsid=74000f95bbaebddb85c80de3c0e70d1f
Good luck!
Matt, April 2009