What about a small piece of velcro? I have the smaller military version of a signal mirror velcro(ed? technology rears its ugly head in spelling) to the inside of my psk. Just about a perfect fit, although, when the mirror's removed, the velcro does attract tinder (lint). Just another feature....
_________________________
Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein