Modifed GT Key
Not for any of the amateurs, but have a look at one of the modifications that can be made to the GT Key in order to add a key ring eyelet.
(Fubar - another mod for your key! :rofl )
drill a 1/16” hole in the base of the lower case where you put the screwdriver to open the case. Then also drill another hole just to the right of it in the corner, and push the small loop of the chain through the two holes, pinch it closed –et voila! The trick is to make sure the diameter of the loop is less than the width of the screwdriver slot – that way everything closes up no problem.