There is a guy on ebay doing fork stanchions for the B1 but at £174 they are not cheap. I have discovered that one of the Z900 tubes fit and if you use the B3/B4 springs they got in without the need of a spacer. They are approximately 30mm longer than standard but still allow (just) the centre stand to do it’s job.
I can get the replacement fork legs for around £90 a pair and I also hopefully will be able to supply the springs too at around £80 a pair.
Let me know if you are interested and I will speed things up.