There are a total of three inside that hub. 2 of them are one size and one is a bit smaller. And now I can't remember sizes. If I ever had specifics on that at all.
But you could look at the website of
www.niagaracycle.com. That's how I got replacement bearings when I needed them. I do recall that one of those bearing was a nine ball in a cage. And I found it there.
Or you might just order a Shimano CB-E110 hub from niagara or someone else. It'll fit your rim and spokes. You'll get it for about $25 or so. It's a better hub and lacing it to your wheel is simpler than many people think.
A youtube tutorial or two is all you'll need.