My eyes were also in need of some help, so I fitted a BSA No8 sight to the BSA Light Pattern pictured below. It's much easier to fit one of these to the Straight Hand Stock with little need to modify the stock except possibly inset the base. This would probably be a good idea as the gun still groups slightly high with the sight fitted as low as possible on the stock. There is a version of the N0 8 sight fitted with an extra short stem but these are almost impossible to find with the much more common short stem being quite easy to source. I also removed and blanked the standard rear sight to avoid interference with the sight picture and fitted a PH foresight globe with interchangeable elements. This means I can use a blade element with a 6 O'clock sight picture as the ring elements would result in a high group on the target. The Pistol Grip Stock requires considerable wood removal from the stock and more careful fitting to correctly align the sight which was something I was reluctant to undertake myself.
I also have an original mounting plate, but there is no evidence of them ever being recommended by BSA for fitting to air rifles and they are extremely hard to find, so probably not a worthwhile option.
The sight has made shooting the rifle at 20yds much easier with the optional adjustable six iris eyepiece making things even easier when indoor lighting conditions are a necessity.
BSA Light Pattern with NO 8 sight.
BSA No 8 mounting plate.
Brian