I have had great results with Blake Sleeves. They are quite thick and the most transparent sleeves I have had so far. Fits MM 2LPs (and even 3LP gatefolds, like the latest Nathan Davis from Sam Records) like a glove. They exist without flap in case you don't need'em. Single sleeves have a little more space but still a very good fit. I don't know how much they cost in the U.S., but I paid $37-38 for 200 sleeves shipped (two unit at 100 pieces).