Found an interesting solution in a google search, I'm not usually a fan of standard fasteners, but in a case like this:
"I've given up hope on finding an M9x1.00. I've called over 20 different specialty fastener places, and even several specialty metric fastener places. This thread is very rarely use, and seemingly only rod cap bolts, and differentials, but haven't been able to get any good dimensional info on them.
I've also got a quote for having a custom bolt supply company at $19.50 each. Yikes.
Used top end for my bike is $275. New cylinder $575, and would need a piston, and all the stuff that goes with.
But, I have decided that I can use a 3/8-24 tap. 24 threads per inch equal a pitch of 1.04 mm, super close to the 1.00 pitch already tapped. The major diameter of the 3/8's tap is .3750 which equals 9.52mm. Recommended bore for 3/8's tap is 3.20, a good hard measurement shows the minor of the tapped hole to be 3.12-3.14. Should be able to tap it right out to the 3/8's." (edited)