Nylon Washers
(115) 3/8" x 1-1/2" od x .060 thk, Fender Washer Nylon
http://www.non-ferrousfastener.com/products.php?cat=205 $0.16 in 1000 quantity + sensible shipping
0.06" thick, which is about 1/16".
(Also consider 5/16" x 1-1/2" od x .062 thk, Fender Washer Nylon at the same URL.)