An update for anyone who is following this thread as well as for anyone who comes across this in the future.

I bought a hollow QR set with skewers from Amazon. The rear axle was shows as having a 9mm diameter. When I checked the diameter of the part received, it was 8.6mm just as I had measured on my existing one. I followd a video by RJ the buke guy and managed to get everything fitted nicely (I had to reuse the drive side spacer from my previous axle as the new one was slightly smaller). As the dust caps with the new kit didn't match up, I removed the dust caps from the previous cone nuts and checked that they would fit the new cone nuts (which they did).