Update for anyone who has the SR 250s and is in the same boat. There seem to be no more OEM Part #: 13033-130331058 left on the planet. None in Japan where the bike was primarily sold. I managed to get the, apparently last one on the Australian continent. Who knows, there might be one or two knocking around in Europe.
The good news is that the small end bearing for the Honda CRM250s fits the KDX250SRs. The bearing is a tad narrower in length, but the diameters, inner and outer are spot on. I have it on good source that the CRM bearing fits, and runs fine in the SR bikes.
I picked up a CRM one, and it looks good to go, apart from being a little shorter in length, and will be used take time I pull the top end. Of course bring the calipers out and measure to make sure of the precise measurements prior to installation.