Couple of years ago I came across a row counter in a knitting shop in Japan. Genius! I did however not think my purchase through, since the counter is not circular needle friendly (FYI: knitting in the round >> back and forth) and I mostly knit with double pointed needles with larger diameter. What to do? Finally I saw a fancier version that met my requirements, so instead of adding that one to my collection I upgraded my old one in a few simple steps
* studded wire/jewelry wire
* few small beads, 2-4
* wire cutters
* needle nose pliers
* circular ring (big enough diameter for your intended knitting needle, eg 7.5mm for knitting on up to 7mm)
* on-needle row counter
Step 1: DIY
Use jewelry wire approx twice the length of the counter.
Make a small loop on the end, thread beads onto the wire (I used 3, the last one fitting snugly in the original row counter), next thread the counter, followed by the counter and another bead fitting snugly.
Now add a small circular loop (mine was a part of a basic DIY jewelry kit), wrap the wire around it. Trim any excess wire.