I looked through most of this thread and some of what I'm about to say has been said, but I don't think it's all been said.
On a 4 string you could do like Paul Gray of Slipknot did and get a set of power slinkys (55-110) and drop the tuning to B F# B E.
The other option would be to buy a 5 string set (and discard the G, leaving you with a BEAD set) or get a 4 string pack like DR's DDT strings, which is a essentially a 5 string set without the G. If you do strings such as these (ballpark 65-130) you could tune the B to standard, then tune UP the E to F#, the A to B, and the D to E.
Going that route eliminates loose/rattling strings altogether (if that is the sound you're going for, I'd recommend going the 4 string power slinky set or something equivalent to that). Just be careful because depending how your bass is setup, the size of your nut, etc. it may not be a perfect match.
My band decided to do some songs in that same tuning and, after considering my options, I ended up just using a 5 string tuned to B F# B E G#.
Hope that something in there was helpful.