Why does it need to be wider? A 3/32" tensioner should work fine with a 1/8" chain.
As tester pointed out, the chain rubs on it quite a bit as it's too wide (the chain that is).
Ah, the chain goes inside the red roller thingy? In that case, I take it back. I do have a lathe, so if you need it modifying to make the channel in the inside wider, let me know.
@Nef started
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Why does it need to be wider? A 3/32" tensioner should work fine with a 1/8" chain.