I lost one of mine quite awhile back and replaced it with a SS 6mm cap screw until I could figure out where to buy a replacement. I paid like $20 plus shipping for a pair when I did find them.
You could use a couple of these for much less.
https://www.patiofurnituresupplies....J2hgkCxjHI9v75lmd1_0rni8VK4x0HyxoCtdcQAvD_BwE