IME you can use a 1.125" with a std shim for the steerer and that has a 26mm open faced clamp which works no problem at all on 25.4mm bars.
I have a stem that is shimmed and 25.4mm. I'm looking at not using a shim.
@bjf started
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IME you can use a 1.125" with a std shim for the steerer and that has a 26mm open faced clamp which works no problem at all on 25.4mm bars.