The crank bearings are available from CMSNL in Holland. Man, they're efficient. I have ordered several parts from them. Last time I put in an order on a Sunday ( Australian time) and they arrived on Friday.
The big end was also shot:
That was a bit of fun to fix. The parts are no longer available from anywhere I could find so... after hours searching the internet and various other catalogues, I found that a conrod from a KTM 520 and a crankpin from a XR400 Honda and a bearing from a catalogue would all fit together to make it work. The KTM conrod is 0.5mm longer, but I don't see that as a problem.
After a lot of work with paint stripper, a wire brush and scotchbrite, the engine is looking OK.
It's all together with a megacycle cam and a little bit of cleaning up in the ports, so hopefully it will go OK.
Looking at the photo, I think I'd better tidy up that bench.