You can accomplish the same thing by twisting the grip material of the handle 2-4 degrees closed. You might have to regrip to get this effect. I suggest experimenting with an old out-of-the-barrell putter, for only the cost of regripping (about $10).
If I find any putter manufacturers that do this, I'll post the info here.
Cheers!
Geoff Mangum
Putting Coach and Theorist
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