you could bar the "D - G - B" strings with your index finger at the 2nd fret and place your pinky on the high "E" string on the 4th fret for the "A" chord. Then you could slide everything up the neck 2 frets and you would have the "B" chord.
Or ... you could try a two-finger B. I just barre at the second fret, then cover the 2nd, 3rd, and 4th strings at the 4th fret with the ring finger. It'll dampen the 1st string, but it's fast and easy to switch to and from in the middle of tune.
LaPatrie "Concert" Larrivee D-03 EP Les Paul Custom Pro w/ VOX Valvetronix VT80+