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Sorry, realised this after posting, unfortunately I don't have access to a lathe though. I suspect getting one made would be costly.
Also my 9mm thru axle fork has a sort of lip above the hubs end caps and without the axle the wheel will happily stand in place. I suspect these "lips" would be in the way of the end caps of a 15mm thru axle hub. Maybe the OD of the end cap is consistent throughout the axle types. Although that seems unlikely given the fact some axles are significantly larger.
It's straightforward to shim down from 15×100 through to 9×100 through, the adapter is just a tube with 15mm OD and 9mm ID