I bought a pair of green Lord's the other day from eBay (probably from the same vendor as you, he has loads of sizes). Warning - these run VERY small! I had to exchange them for a larger size, which just arrived today. Get at least
1/2 a size bigger than normal and consider a full size up. I settled for 1/2 a size up on the exchange and think it's OK, but YMMV.
They're technically house slippers in my opinion, but I'm also considering wearing them with black tie, just for kicks!
(/waits for combined onslaught of the black tie purists!)