Doug didn't like the Photon for use in the PSP, because it turns on when squeezed, so piling stuff on top of the PSP can drain the batteries, etc. You might use the $1.00 Countycomm lights instead, which have only a slide switch, no squeeze switch.

Another thing I'd do is replace the tiny pencil with a regular thickness golf pencil, which can double as a handle for the scalpel blade. I might pre-cut a notch in the golf pencil ahead of time, for tying wire to.

Water carrier: use a 1 liter ziploc freezer bag, folded up.

There was a thread with some other suggestions like this when the PSP first came out a few months ago.