My old socks were starting to wear out (mostly tearing around the ring), so I bought 25 socks (minimum order) from filterbag.com. These are 7x16 200 micron polyester socks with a polypropylene ring. They are singed on the outside and soft on the inside. They are quite a bit more flexible than my old ones, which were polypropylene with a singed interior and exterior. They cost me $97 shipped, which works out to $3.88 each.
Here they are:
Here they are: