I think Kipp makes very high quality in large variety including with a stainless steel bolt. You want the 6 mm 30 mm long if you go with theirs. Getting stainless bolt adds to the cost but they are the only ones I have found with SS bolt. There are many cheap ones and they will work but they claim to be aluminum but the bolts are carbon and will rust. I paid about $25 shipped for mine but I can't remember the supplier. You also need a nut with Kipp. Theirs don't come with them.