[Closed] 11t cog replacement..

I have a cassette that i have used with a new chain - yes i know lord strike me down.. but the cassette was really in good condition apart from the bottom cog. Went out other day and all was fine apart from the 11t, which slips every so often, now i know i shuold buy a new cassette but i would like to get some more wear out of this one, is there anywhere where you can get just the 11tooth cog to fit a shimano cassette? Would be grand given the prices of shimano now!