Leg Bands issue

[valschicksrus]

I found the place where many of you talked about the leg bands, the use of zip ties etc. How do you know the size to purchase ?? My chicks are still young- 3 mos I think, but as adults (Orps & Wyandottes) what # do I order??? I don't want to keep the zip ties on, would rather have a numbered band on them.
I live in Calif. so where is the closest place to order from? Thanks