That's not a common breed to find from a private breeder. Sounds like a breed you may only find thru a hatchery like Cackle Hatchery, etc. I've never heard of any feed stores carrying rare breeds either ~ mostly just layer or production breeds.Hi any one have Dorkings for sale in in Marysville.
Check this BYC thread which might help w/ breeders lists/references. There's a Dorking Club website & a Dorking group on Facebook. Good luck:
https://www.backyardchickens.com/threads/the-dorking-breeders-thread.882047/page-49