If you cannot find an original stock for sale, you might want to try contacting custom stock makers here in the US to find one who has duplicating machinery and would be willing to take on the project.
Then you could advertise for someone who would be willing to let the stock maker borrow his stock as an exemplar for duplication. This works on a couple of levels. Once the stock maker has the dimensions programmed in, he can make 2 stocks as easily as one so the owner of the original could get a spare. If you offered to pay for both it would sweeten the deal considerably.
Warning: this is NOT going to be inexpensive.
Edited by StrangeRanger, 18 December 2020 - 05:34 PM.