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"...10-40 3/16 set screws..." Those are an odd size for scope bases. They're usually 6-48 or 8-40. Brownell's sells a package of 12 each with different heads of 6-48 and 8-40 x 3/4" for $12.45US.
Your local gun shop will likely have scope base and filler(set) screws too. They might just give 'em to you as well.
When I was looking for set screws to accurize a CZ 452 Varmint I was directed to a location in Burnaby. Just about every major city has a business specializing in "Fasteners". If you go to Ukrainian Wheel of Home depot, check the address for the supplier on their products.
I checked 4-1-1, Locate a business.
In the category I entered Fasteners and screws, and narrowed it down to an area Code. There were a number of choices, and the one I had gone to was Pacific.