Hey dude, we haven't got any of the allen head ones, but we have got some of the two locking nuts with the locking tab washer ones, the sort they had on splittys, could chuck a couple in the post if they are any use?
As my post they cost around £15ea new from most suppliers.
I have 3 of the same side as los the matching (other) side so if you want one it is £4.50 posted or £3 at Slough -you'd then have to source another second hand or pay for new.