Shown below are the bluetooth adaptor before and after modification.
Step 1: Dismantle!
Get some wire-cutters, on one piece of plastic, cut along the red lines, as shown below. On the second, cut the corners off so it looks like the second picture.
Piece the whole lot back together, and it should look somewhat like the last picture (Red being what it was before, Black being what is is now.)
Step 2: Chop, Chop!
Look at the picture before you do any cutting!!!
Get a saw (I used a hacksaw) and cut two cuts down the side of one brick, as close to the edge as possible. Use pliers to twist and bend it 'til it comes out.
Use wire-cutters and pliers to take out the centre-piece.
A knife and file should be used to neaten it off a bit, until your bluetooth gadget will fit in.
Repeat with other brick.
Step 3: Glue, What a Sticky Situation.
Leave to dry.
Leave to dry some more.
Step 4: Make Cap (With Another Lego Brick)
Cut two 1-2mm (thick) pieces, big enough to fit on the top and bottom of the brick, as in the picture.
Glue them in place. The USB bitty should fit in nice and snug.