UPDATE-after contemplating solutions(thanx Guys for all the help !)i went for Aquaseal.
After 18 hrs curing time i put the boots on-and they are"as new".
Tried in puddles,no leak.Looked at the patch after 15 km wearing them in the bush-patch is same as the day i put it on.........Awesome.Hope it will last a while.
Cheers
GBK