The one way clutch Part # is 72098526. A search of the web turned up nada. I did see a thread indicating it was no longer available from the factory. As I remember it they were around $6-800 in the 90s, I have heard of them going for close to a thousand in more recent years. At that price it seems like the chi-coms would jump in and provide replacements that last 1/2 as long. Must not be a demand. It involves a complete separation (3 pieces) of the tractor to remove the transmission housing. Normal procedure is to replace the clutch related parts and resurface the fly wheel while it is apart. Also the engine seal. If you find the part and all the other parts needed to do this you could very easily be looking at a bill much higher than the value of the tractor. A senario I dread as I have had mine for 18 years and love it. Fortunately this will not be the part that turns my tractor into a parts tractor. I have one in my spare parts box.
Curious, how many hours you have on your E-280 when the clutch went out?
Good luck, let me know if I can help.