I'm not sure where you could get it from, but as far as I know its just a silicone elbow, make sure you get one thats suitable for oil though, as a standard one will degrade over time and leak.
Otherwise, if you can't get hold of one, you can use a piece of hose inside the existing return line, then clamp it up tight and that will do the job just fine. Remember its not under any pressure so you don't have to worry too much.