It seems to me that one of the reasons for the long bearing assembly in the water pump snout, and the lengthy bearing assembly (that Doug showed in his picture, a few posts above) is to react the sideways loads on the water pump shaft caused by the belt tension.
Nevertheless – if you could find robust bearings, you could mount them inside a shortened sleeve (with a slight interference fit for the whole assembly). This would require very precise boring for a consistent fit.
Or you could just make a spacer tube (like a crush sleeve) that fits between the two bearings.
The shaft, seal and the inner bearing would press in from the impeller side, and the outer bearing would press in from the snout side.
It seems like the seal is the most critical part, to keep water out of the whole assembly…
But all this is just a guess from looking at Doug’s picture.
Doug - if you take the snap ring off of the non-sealed side, can you get a puller on the seal & both bearings, or mount it in a press?