i know the clymer book says to use the valve adjustment tool, but, really, if you can't find one:
use a ratchet with an extension, loosen the nut,
insert your feeler guage (45 degree ones work best)
adjust your screw accordingly
if you tighten the screw, dont tighten it all the way til the guage is snug
tighten the nut and as the threads clench, the nut will turn the screw the rest of the way (<1/8 turn)
not really the reccomended way to do it, but, after some practice, you get the feel of it and won't need the valve tool
OR
if you have a 12mm (i think) deep well socket and a thin flat head screw driver, you MIGHT be able to grip the socket with a pair of channel locks and fit the screw drver down through the middle of the socket
(which is essentially what the valve tool seems to do (i haven't bought one either)
just make sure to double check your work and be PATIENT, it will take a few tries to get the feel for it