The other day I had an email about sourcing quartz movements, and since I found the links I'll post them here from others. If you're looking to buy a quartz movements, these are the biggest sources right now.
There are others, leave a comment if there's one I should add and I'll do so.
In terms of availability and cost, the Miyota and TMI are probably the easiest to buy, with the Swiss (ISA, ETA, Rhonda) varying in accessibility. It seems to be variable, as part of my consulting work I contacted ETA for a small-volume purchase and they responded promptly and even sent me a handful of sample movements, so don't hesitate to try.