They just can't be _that_ special...
Even a boutique maker like Zon and whatever bridge they use are going to have 'standard' small-parts hardware.
I agree hardware stores are going to be fairly useless - where OP needs to go is a hobby store. Maybe some place catering to model makers and slot cars.
What you might be able to find in a big-box hardware store is a thread gauge - if you can narrow down the size and the pitch (and maybe the head style, although they're virtually certain to be inhex ("Allen") ...), the rest is pretty easy. (In the unlikely event the screws have Torx heads, you have determined that they're not metric - for some reason the Torx concept doesn't seem to be available except with 'English' threads.) But I don't think I've ever seen a set screw that was not either inhex or slotted.
Since teeny set screws have to be very strong for their size, they're almost all heat-treated. Getting a bit of rod threaded with the right pitch is easy - heat treating afterwards not so much...