Many readers of this blog will be familiar with Ilford's annual Ultra Large Format (ULF) production. Some of the films they make can only be ordered once a year, and they only make them if they receive enough orders.
One
of these is bulk (50') rolls of 46mm HP5+, which you can respool onto
127 backing paper. I just heard that Ilford doesn't have enough orders
for this film to produce it this year.
Freestyle Photo still appears to be accepting orders, but this could end at any time. The relevant page is here.
I hope this information is helpful to you.