I have a product for the laser that'll work just fine, I think.
It's about .005" thick, got adhesive on the back, and it's stiff, not flexible like vinyl. Send me the file and I'll cut it for you for free to see if it works. You'd have nice, individual letters with a strong adhesive on the back (not that that matters, since it's not but so much surface area on a 1/8" tall letter anyway).
PM me and I'll get you my contact info.
I've got some white I use all the time for different applications. I cut through it, leaving the release liner in tact. All you'd have to do is put transfer tape on it and you should be set.