STX,
Man if I had my heart set on a 20 ga Pardner, I would be using all my resources. Call Pawn shops, Hardware stores, look under FFL in phone book. I don't know if Dicks has a special ordering program, Walmart or Kmart maybe be able to help. Quick had a link to Walmart special order, but I don't have it anymore. It maybe time for a road trip to Basspro in Springfield, MO. The only experince I have with a 12 ga. single shot is with a Sears Ranger (H&R M-48) In my younger days I used it for squirrel hunting 1 1/8 oz game loads. I wasn't to happy with the recoil. I used it this summer to protect the sweet corn one time. I used a 2 3/4 Magmun lead #2 for a raccon, after that the Little 20 ga. went into service.
Good Luck and Find you a 20 ga.
Froghunter