I've been hunting high and low for years for replacement options for the stock bolt that comes with the m970 cranks. The only option I'd found was the yumeya option, but both they and the standard one are scarce to say the least.
I'd almost given up on finding any aside from buying cranks just to get the bolts when Eureka, I found some aftermarket ones located in Australia.
A kind RB member helped me get them to the UK, as seller wouldn't ship to UK due to Brexit rules and regs. I've kept some for myself but bought more than I needed as I though there may be others looking for replacement bolts.
They are pretty cool, carbon fibre inserts and not just the nds bolt but two bolts, one with a compression assembly to blank off the open drive side axle.
I'm after £20 a set Inc UK postage. Will discount if you want more. I've got 6 sets to sell.
Pics below.