When repairing spinning wheels, I like to stick to the same materials that the wheel was made with as close as possible. Even more so with older wheels as they didn't have time to muck about with repairs as this took time away from spinning yarn. They choose the longest lasting materials for the use they had.
For a bearing to hold the flyer, I prefer leather and often get an old belt at the second-hand shop and cut this to the right shape.
I'm not sure sugru would be ideal as I find it's quite brittle and doesn't wick up the oil as well as leather. In general, the older the wheel, the more oil it needs. Sugru can also get stuck in the
wood so when it comes time to replace it (because these bearings wear out and need replacing - even the modern high polymer plastic ones) it might have trouble getting it out of the wood.
Anyway, I know this
project is past that step but I wanted to check in and see how it's going. Did you get a new flyer? Were you able to get some photos? Repairing spinning wheels is a passion of mine, so feel free to ask if you have any questions.