I've just approved a bitcoin bet on the existence of a such a miner:
mtrlt has a fast LTC GPU minerYou are welcome to place your bets.
You can also PM me if any evidence surfaces either way.
If you change the bet to generic "will a LTC miner capable of running 250 kh/s on an 6990 be proven to exist by March 1st 2012?" and allow anyone (not just CoinHunter or mtrlt) to provide the proof, then it could be a bit more fun.