Just tap around the outer edge with a hammer and they should work their way out. Sometimes they come right out and then again sometimes you have to work at it. I haven't bought a pair in a few years but think they would be in the $20-30 range. Auto Zone, ORielleys, Walmart ought to have them. Just take one of the old ones with you so you get the same size.
You may want to tap them in with a hammer, there is not much too them, a grease zert, spring and cap. When we clean and repack the bearings during the winter, we do the same with the buddy bearings. Is the grease coming out between the hub and BB or is it coming out around the edge of the BB and the spring and cap? Mine push grease out the end near the spring and cap we just clean them up and pump more grease in.
Your bearing buddies are leaking? Thats strange. They might be comming out (which I highly doubt it) or might need replacing. If theyve been on for quite a few years might as well invest in some new ones for what they cost. I had some on my jetski trailer and they worked awsome, never had a problem. If you take a rubber mallot and lightly tap them on the side they should come off.