I always had them made by my shirtmaker. I used SGA and was very pleased. They used to have their own very small retail shop in NJ, possibly Millburn, but they mostly sell through retailers as they are a maker.
LS in Manhattan handles their line, if you travel there, you may wish to consider them -
They make on Ferry St. in Newark NJ. If you can't locate a convenient retailer, you might try to get a phone number for them, and ask for a stock list. -
As with any MTM or Bespoke service, the quality of what you receive is highly dependent upon the knowledge and experience of the retailer with the maker.
I'm fond of pinned collars, but found I preferred them made to purpose with eyelets. Skip designed a slightly elongated club collar at my request, as I needed a slightly larger collar to balance my fairly large head. I preferred them with 1/4" tie space, as I did all my collars. The slightly larger collar also assured there wouldn't be problems fitting a knot in the available space, though I try to tie small ones.