I second tying on a normal counter. I often make my tally marks on my arm or back of my hand if they can be transferred later. Or how about those bracelets with coloured beads like an abacus? Very simple and portable.
There are two rows of beads in different colours going around your wrist. E.g., black on top, white at the bottom. There's also a piece of elastic tied into a small loop. This tiny loop goes around both strands, kind of tying them together (but not tied, just a stretchy loop).
Every time you finish a row, you move one of the black beads over to the other side of the elastic loop by stretching the loop and pulling it over. Every time you do a tenth row, you move over a white bead, and return all the black beads to the original side. So for every white bead you've moved, you know that's ten rows: 3 white beads = 30 rows.
And for every black bead, 1 row: so 5 white beads and 7 black means 57 rows.