It's hard to say just from that description, as there are a whole slew of red cowpeas, starting with the venerable Red Ripper and its clones: Little Red Ripper and Red Ripper Improved and Big Red Ripper.

There's a Kentucky Red Pea, and a Red Wonder, and Fusion just sent me Franklin Peas to try, which are a fairly large red pea.

Crudup is a very dark red, but is incredibly rare, so that's likely not it.

Two suggestions: Their lack on the shelves may be a temporary thing (like they're out of stock, or there was a shortfall this year). Keep checking. If you find them, use the commercial stuff as seed stock.

Second, investigate joining the Appalachian Heirloom Seed Conservancy. I'm confident some of our members know exactly what you are looking for, and have seed they can share. You can reach AHSC at KentuckySeeds@hotmail.com

FWIW, all cowpeas and crowders share the same scientific name, which is Vigna unguiculata.

Hi Jotuna,
The Southern Seed Legacy has lots of photos of heirloom cow peas. They do have a Red Pea listed.
http://www.uga.edu/ebl/ssl/activities/seedlist/

And did you find this food product on the link below?
Remy

Here is a link that might be useful: Carolina Plantation Rice Red Peas

Many thanks for your followup gardenlad and remy! My patience is always in short supply; could be those peas show back up on the shelves. Meantime you've both given me some good places to explore, the Carolina red peas especially since they're in the state. The Hoppin' John I made today just didn't seem the same with black peas...

Haye's Field Peas are the most popular pea in the Low Country. Haye's Field Peas turn dark red as you cook them. The peas are packaged in Greenville, S.C. If you know of another brand please let me know.