You have given me an idea (always scary).
Combine Fisher Space Pen Refill with pencil in a survival sized form factor.
Presently Fisher makes a compact one which has either a bullet style or a pull up style expansion "rod".
Now just either modify one or take the refill and somehow add a mechanical pencil to it. It would still be smaller than a golf sized pencil and give you write in the rain ability as well.
A little shrink tube, a little old pencil, maybe an old clutch type pencil with 2mm lead and your there.

What's the market, both survival and "wallet" use.