I would think that it would be a standard off-the-shelf size bearing/bushing. The ID is 3/8" and the OD should be either 7/16" or 1/2", after that all you need to know is the length. Once you have the ID, OD and length, if it is a standard size a part number for that can be found easy. An Oilite bushing like that is probably between 0.50 and 0.75 cents. When I replaced the input shaft on my Cub it came with the new bearing/bushing installed so there was no need to replace it, and I did not bother to measure.
Where you are, right now, is of absolutly no use unless you are able to get away from it, FAST!