The 2031P models appear from time to time on Ebay and Craig's List. Not as popular as the "A" version but they are out there. In fact here is a pair here:
http://www.ebay.com/itm/Behringer-TRUTH-B2031P-Passive-2-Way-Reference-Studio-Monitor-Speakers-/182011020467?hash=item2a60b3c4b3:g:O~gAAOSwvUlWr9j7
I'm looking for a pair myself to handle the surround channel. Probably overkill for surround but a decent Polk Audio book shelf set is about $117. I'm thinking I can grab a used pair or 2013P models for the same price with the added flexibility of changing them into a separate pipe rank channel if I wish. Plus aesthetically having all matching speakers is kind of cool.
Danny B.