I don't know where the cheapest place is. At lessemf.com they sell a sample packet of fabrics, and if you place an order they credit the full price of the packet to your order. So it's like you're getting free samples of about 40 fabrics.
That said, I don't agree with using fabrics. I think they may distort the EMF and some people think they worsen it,.
The best solution is to make big lifestyle changes that gets us as clear from EMF as possible. Usually that means having some kind of big change in heart, which is a different process for everyone.