Cad is going to be difficult where your located - unless you ship them. Ever so often someone starts doing it then gets shut down. If you want to ship there are a number of recommendations in threads on the site related to the subject.
Zinc and dichromate can be found at a fair number of places since its not a big hassle like chrome and most of the quality comes from the part you start out with or how you or they prepare the part.
Shops will use the basket or wire tie methods. Not as many using the wire since its a bit labor intensive but you can talk to those platters and ask them (if it will "help") for them to just leave them on the wire and you can remove. Did that for over 20 years using a local platter
Used a place in Fresno (not sure how far that is from you) last time for zinc and dichromate- since you pay a minimum had everything done in dichromate then once I got the stuff home stripped off the dye to just leave zinc on the piece I wanted finished that way. Not for everyone (there is a thread with pictures about the process) - I'm just frugal at times
