Not sure where in Fife you are but around here I can think of two small places that you might try, one on Falkland Estate just along from Pillars of Hercules, does woodturning and furniture but there's a forestry operation on the estate too so either might. Or at Den of Lindores by Newburgh there's a specialist wood mill run by Dennis Anderson.
Volume might not be enough, but failing that just buy a bag of shavings from any agrimerchant that supplies stables, that's what I use and a bag of compressed dust-extracted shavings a. lasts a long time and b. is less dusty for the chooks than commercial sawdust. I get mine at Collessie Feeds, Newton of Collessie..