Best to just measure the old ones, but usually 1" caged bearings are 1″ Headset Cage (5/32″ Bearings) : 37mm Outside Diameter
It seems this is the case! 5/32, 30mm inner diameter and 37mm outside diameter. In total 16 ball bearings.
@TooTallTim started
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Best to just measure the old ones, but usually 1" caged bearings are 1″ Headset Cage (5/32″ Bearings) : 37mm Outside Diameter