I came across a useful item while combing through eBay. It's a Butcher, Sheffield 5/16" bolster mortise chisel. Buy it Now price is $14.99. The handle has a split and the back needs some flattening, but this is still a very good price for one of the more useful sized chisels.
Auction Listing Link
I'm not sure if 'one of's' are permitted in here, but this one should go to a FW member !