Try eBay for bearings. Search for foosball bearings and lots of different styles, sizes, and shapes pop up. Maybe one will match what you need.
To clean rust off the rods, crumple some aluminum foil into a ball, sprinkle some water on it, and rub on the rod. Should get the rust off without scratching the rods. If the rust is more than superficial, there will probably be some dark pits remaining but the rods should still slide smoothly.