I just made a home-made inka.

1) cut a scrap of 1/2" PVC pipe to length of 5.5".

2) drill a small hole at one end of the pvc.

3) put a key ring through small hole.

4) Jam a Pilot G2 07 into the pvc pipe.

5) attach to regular keyring.

The G2 fits just snugly enough to not fall out but not get jammed. The 5.5" length keeps it from writing on something while in your pocket or bag.

Other pens may also work. If they're too large to fit inside the pvc, either get bigger pvc or clip it on the edge of the pvc like a pocket. If too small, add some elastic or something through the drilled hole to take up space and add friction.

If the PVC is too boring, remember it is possible to find colored pvc in some places (used for making furniture I think). Or wrap with an old scrap of leather, or braided leather or braided gimp. Braided color string?

Next year I may add this pvc pen-holder to my pocket calendar. I usually buy a cheap 3x5 weekly calendar to carry around with me and mod it by reinforcing the cover and covering with an old piece of leather.I could put the pvc next to the spine of the calendar and cover the whole thing with leather, then I'll always have a pen with my cal. UInfortunately the G2 is a bit more than 5" long, so the pen holder will stick out a bit.

Or maybe just put them both on the same keychain. Yeh, keep it simple.

For the HPDA freaks, I have a bit of elastic along the spine of the calendar (loop goes under the leather) that I use to hold folded 3x5 index cards. The cards keep my place and the elastic keeps them from falling out.