Brownells sells the rear sight and parts to it but not the base. I found sights to 77/22s on eBay. If you knew where to talk to a gunshot that was in business back in the 80s, they might have a used one that they took off. I know how it is finding parts that are no longer being made. I will look some more. I think my old Ruger came without a base, but I have been planning to get it out of the safe and put. a new scope on so I will look there also.