You ought to say what City you are in to narrow it down
United Diesel
(626) 579-4832
1903 Penn Mar Ave, South El Monte, CA 91733
I worked there as a temp replacing a Hospitalized Employee. That was around 1989. It is a big shop and has been in business since the 1970s.
If you can't go there perhaps they could ship to you.
Note there is several generic European companies that supply entirely adequate gasket kits for Bosch and other Fuel Injection Pumps. If united diesel cannot supply you with the real Bosch ones they can likely have the generic ones.
Ask for delivery valve crush washers and give any other info you have and the Bosch part number. Tell them it does not have to be real bosch.
Note don't let them think you are like taking apart your Pump. Tell them you need to replace the crush washer after you drip time the pump.
This place might be in Canada. The are 5.99 in Canadian dollars.
https://www.laundrybagh.com/index.php?main_page=product_info&products_id=279407