From the 1989 MC18 R5/6k onwards the crankshaft bearings and seals are the same for all models I believe.
So that's all MC21 and all MC28 as well.

LH crank seal 91205-KV3-771 25x38x6
RH crank seal 91203-KV3-681 36x68x8 (also 91203-KV3-831?)

The inner central crank seal is an integral part of the centre main bearing of course.
The inner central crank seal/bearing does not have Honda part number as it is part of the crankshaft assembly.

The outer central crank seal is an O-ring. It has Honda part number 91301-KV3-771
Big end bearings are the same as for a 2012 Honda CRF150R being 25mm ID x 32mm OD x 16mm wide. Pro-X and Wiseco part number 22.253216F

For more info see this picture.

These parts are becoming harder to come by as time goes by, it seems.
Hope that helps.
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