Creative use of sockets and a bolt .....
You need a socket larger than the opening and a bolt long enough to run through both bears, a washer and a nut. When you tighten the nut it will force the bearing into the larger socket. A small length of 2" or 3" PVC with a plate with a hole for the bolt or large washer would work. I'm thinkin a 1/2" bolt would fit through a 1/2" socket..... ?
MacGiver this until you get it done!
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)