Soltek don't sell their SFF's anymore in the U.S. as they pulled out of the U.S. market. Newegg was the last known reseller to Soltek's SFF's. Nowadays stores don't want to have to deal straight on with Soltek because the shipping rates are insane and if you want to save some money you'll have to order a bunch of SFF's. Which most online stores these days don't want to risk.
Needless to say it's close to impossible locating a Soltek SFF in the states. If you do. You'll be paying a lot of money for it.