Bill Tindall, E.Tn.
Our county government ag office sells partial rolls (office has some initials like FSA or some such). Probably many of these offices do.
But, it is not necessary to put under pavers in typical environments. It is helpful to resist hooves punching through compacted crush rock- feeding pads, creek access. You will never get a punching load on a sidewalk sufficient to drive a brick into the compacted base unless it is mush beneath. Out pavers are on a sandy river bottom soil. A few inches of compacted ungraded crushed rock, couple inches compacted sand, done. Has been stable for 2 decades.