I use something cheap I found on ebay from hong kong. 1kg max pocket scales.

That said, I only ever use them for getting a rough idea of front/rear weight distribution. For left / right I lift by the shock towers, and for de-tweaking I set droop with a gauge + use the lift technique. It just seems easier and more reliable. Whenever I tried to balance or de-tweak with scales, it just seemed like they were too finicky, and I'd end up making things worse.

-Mike