How about a keyring that resembles a very mini version of the Isis. It would be a great addition to the range, and would look great on a set of keys. It would also make for a pretty good marketing tool.
I reckon an aluminium replica of the Isis about 2cm in diameter with a key chain on the opposite end of the plunger. It would look very cool.
And something even cooler would be an Isis Mini - a regular Isis, but about half the size. Followed by an Isis Nano - about the same size as the key chain, but fully functional
On a serious note, though, the keyring would be very cool.
I tried to knock one up in Photoshop, but found it quite difficult to do - mainly because I don't have photoshop installed