I'll second MBS model supply. I use his sleeves and eyelets as well as his crimping pliers. Just so easy to order 25 or 50 sleeves and not sit and cut them all (lazy I guess).
Another source of the sleeves are fishing leader sleeves. I found them to be hit and miss. Some were really nicely flared and needed little clean up but others took as much time to flare the ends as if I had just spent the time to cut them myself. Once I found MBS I stopped chasing a source of good sleeves.