White is unusual. Most is Green/yellow or brown. Maybe have a look on ebay to see if any on there. I sometimes find rolls of the common sleeving at boot sales at about 10 pounds. Lasts a long time as it sonly used in 4 inch lengths.
In all the years i worked, i had never bought a white roll.
Could even be railway sleeving. I will ask the boy who does signal wiring if they have any.