I could send you a stainless top bolt, if you're interested. I have an entire box of M6 x 40 SS cap heads-- I need them, as I am addicted to making my own gap caps. Seriously, addicted. I can't stop. If you might want a neato top cap, I've started passing those around too, in a sort of pay-it-forward type of deal. Given away about half a dozen of them to date. Just a very few examples (as I've made ~40 so far)