$42 for 2 modified seatpost clamps is INSANE! I hate how xtracycle gouges us. $4.50 for one shark fin snap piece? Anyway, I found this:
Just thought I'd pass it along. Not bad for $4.20 each. They don't fit perfectly (too loose) but I made them work with a little bit of gaffer's tape. I think an old tube as a gasket would work better but I didn't have any on hand. I ordered another 2 to round out my attempt at 4 pt security attachments. Now I can lift the tail of the Big Dummy with the massive Nuvinci back there from the snap deck and not have it pop off.