I was at WallyWorld last night and found a nice, rather inexpensive little key chain pen made by Zebra, model F-301, it has a loop for a split ring, two to a pack for around $3.98. Its not a Fisher but for the money its not bad. The Fisher is selling for $22.95, I'm curious if maybe the cartridge from the fisher will fit the Zebra, they look similar, I have a couple Fishers so I'll try it.

Well I just tried it and its so close its not funny, the hole in the tip of the Zebra is just a tad smaller so some day when I have time I might try to enlarge it.