I need to edit my opinion. Semi tubular rivets are for joining where movement is required or allowed. Not for a tight clamping, Tubular rivets are what you need for this part. Aluminum tubular rivet. A solid rivet requires much more force, you are liable to damage the semaphore and they are not necessary for this type of assembly. Brass will work also. both softer than steel or SS.
If you want easy DIY and don't care about originality, use pop rivets.
A short semi tubular rivet will be like a tubular rivet anyway. The problem is that when the hole in a semi rivet is not at the right depth, it won't upset right for your grip length, The rivets are sold with a grip length range not exact.
Another thing is you have to buy a 100-150 at a time unless Ace or someone has them.
