This article is from the Fitness FAQ, by Jeff Gleixner (firstname.lastname@example.org) with numerous contributions by others.
They sell a set of 6 weights: 1.1 lb; .55 lb;
.275 lb (fractions of a Kg, 2 each weight) for
$30 plus shipping, in case anyone else is
interested. Or you can buy them individually for
$5 apiece ("for cost of machining them", their
Grover Furr email@example.com
From IRONMAN magazine
Ironman Products 1-800-570-IRON ext 3.
1 1/4-100lb Olympic weights machined 10lbs/$10
1 1/4-100lb Olympic weights $0.55/lb
Bodybuilder's Discount Outlet (708) 268-1611
Many more exist. Check local fitness stores.