Yes the B2 is an awesome sounding bass module but it can be challenging to carry around. I had one that came with my L1 Model 1S and I purchased a spare B1 so it would be easier to transport.
As far as resources for B1s, I've had success with Reverb and eBay. You could try selling your B2 on the same, but you would have to pack it up and the shipping could be expensive. I've sold some gear to my local Guitar Center, but their margins won't allow for much of a trade-in value. If you're lucky it might come close to a wash if you can find some used B1s in decent shape at a fair price. You could also try Craig's List and your local music store. Who knows, maybe someone on this forum is looking for a B2 or has some B1s for sale.