Well, I'm using one of these: and it works nicely, but you need an UltraSCSI card for it!
I have had great success using the Kingwin trayless bays for both 3.5" and 2.5" drives. But the ones I am using are mounted in bays in the PC, and I think that you only want external ones. Since Kingwin has been very good to me, I suggest that you look at this if you have the bays and this if not. The latter claims to do hardware raid within the enclosure which may be more fuss than you need, but it's a good brand.
I used to have links to exactly what I think you want, four or five disks in a dumb external enclosure that supports port multipliers, but they are broken. I'll add on if I find those products.