Aren't those on sheet E-10 of the NSR250R2J/R4J [R5K/R5K-2] 88/89 in the Online Parts Manual of nsr-world.com?
At least the l/h and r/h seals are there, as far as I understanding there are no Honda part numbers for the bearings and the centre seal themselves because Honda considers the crankshaft not to be servicable.