Looking for John Deere Model 40 roto tiller sproket

[DKO3677]

I am looking for a John Deere Roto Tiller, Model 40, 1979. upper chain sproket.

 

[Tinhack]

If that's a picture of one, it looks like it would be easy to make one with parts available from Tractor Supply.

 

[MTGreen]

Or surplus center. Weldable sprockets on hub