Chris,
If it helps, I can recommend the type I purchased several years ago when I first got into MF film. It goes by the name of
Ar-Kive sleeving and can be purchased online from a place called
Climax Photo and Digital, at a lower cost than the (perhaps more familiar) PrintFile or Lineco brands. It is quality archival sleeving which Climax sells in a wide variety of options - as pre-cut strips or in bulk rolls (either perforated or not), in two different grades, and either clear or frosted. I have been very happy with the roll I bought.
If you happen to live close by I would be happy to cut you a length sufficient for a few rolls. Otherwise, buying a bulk roll from Climax is a pretty cost effective way for you to get what may be a lifetime supply.
Good luck!
Jeff