For premium plastics, there are some for sale both by vendors and privately as well. They are not "custom" but some might be able to be "customized".
@The Chip Exchange (Vendor) has a few lines of Bud Jones chips, such as Intercontinental San Juan, for sale. Check out their President's Day sale thread for pictures and prices.
@liftapint , a long-time member here with one of the highest positive feedback ratings on the site, has some Emerald Bay Matsui chips for sale (from a recent large forum group buy) in Classifieds.
Myself, as a temporary Vendor, I have some Bud Jones S2 chips from the defunct Big Easy Casino casino cruise operation, available in sets.
There may be many other private sales in the Classifieds. In recent memory I know there are more Bud Jones V7 series, etc.
As far as number of chips to get, most people think they need more chips than they probably do. You'll need to define what sort of games you play (cash, tournament, or both), how many people/tables at a time, cash stakes/tournament structure and how many typical rebuys, and total budget.