I have tried the same thing, downloading some combat tracker in the free downloads section and laminating them...
works just fine, but I have to replace ours frequently because the dry erase tends to stick more than I would like and beer stains...
one of my players is notorious for spilling suds at the table, even when we made him keep his on the floor, he knocked over someone else's beer!! I mean every session (1/week) he is good for at least one!
Ah well...
Good luck and that should work just fine for you!