Dear George,  Bellows material may be purchased from any clock supply
house.  The four main ones in the US are

 - Merritt's Antiques (www.merritts.com) has it for $4.25.
Item no.  P-1432

 - Time Savers (www.timesavers.com) has two types.  paper, which is
used in most cuckoo clocks today, item no. 20168, 12"x12" sheet for
$3.00.  Leather, 30 sq. inches, item no. 18936, for $15.00.

 - S. LaRose (www.slarose.com has what they call "bellows cloth",
8-3/16" x 26-3/4", item no. 085256, for $3.95.

 - Black Forest Imports (www.blackforestimports.com) leather,
item no. ABL 6"x6" for $6.40 or paper, item no. ABP 6"x6" for $1.80

Vincent Morgan, NY City