I have a few made now for sale $22 to your door in the US. Primed and painted...ready for your favorite book!!!
I can drill them too but some wheels set different on the carrier so best to fit/drill it yourself matching the existing hole.
The "Key" goes into a slot as seen here. You may not have the slot (post 67?), so check first:



On ebay right now: http://www.ebay.com/itm/251338743908?ss ... 1555.l2649



