As I understand what you have, if the shaft has worn through the bearing/bushing into the housing, the shaft is probably grooved. The grooved shaft will chew through a new bushing fast and you'll be back in the same situation that you have now.
If the shaft can be smoothed down, then it might be practical to have a machine shop built the housing back up (by welding) and have it machined out to hold a new bushing.
Several options for you to consider. If it is external, you may be able to replace it with a pillow block ball bearing that fits the shaft.