Thank you everyone for the advice. I'm going to try the nail varnish first, since my wife has it already. Plus it would seem to lead to the smallest profile on my keys vs. heat shrink tubing.

Thanks for the lead Roarmeister -- wish I'd known about the smaller version before I bought this one.

I find the three thousand strike claim funny for this purpose -- I'm only carrying it for the random emergency -- it would work fine if it was totally reliable for ten fires, for instance. But more is always good, right?