I made juggling balls for my brother as a Christmas gift last year. Then I decided that I would like to have ones for myself as well.
I made the pattern myself, but here are very good instructions, if you would like to make ones for yourself.
They are not actually round, but a bit square. This, I find, actually makes them easier to catch. Mine are stuffed with linen seed, but you could use any other grain as well.
I don’t know why they all look a different size in these pictures. I used the same pattern on all, and measured the stuffing. Odd.
Now, I can’t actually juggle, yet. I can manage maybe 5 throws, before the balls escape me. But I’m trying!