Thanks for the responses, everyone. I've been on the lookout around town and was unable to find any store that had these or end bolts, and I checked about everywhere, from arts and craft, to hardware, to gun stores, to no avail.
I just looked at their supply and unfortunately it looks like the screws they stock aren't quite the right length; it looks like maybe a #1 screw, but an inch long. Maybe someone else has some...
I'm afraid I might need to go this route, so perhaps I can purchase some other wares from him to make it worth the shipping across the pond.
I wish I had started playing earlier then! It's not so much an issue with the thread, like you say, nor the screw hole, but the head of the screw. I had read previously about the matchstick trick, but it will stay a trick until mine starts stripping out the screw hole.