My LBS does not carry fixed-gear/single-speed parts. What next?
Your local bike shop may not get it with fixed/single speed but do not discount them entirely. They can sometimes compete on price better than a mail order company simply because they will not be charging you shipping even if they have to get parts in specially for you.

Most bike shops have at least a couple of regular suppliers and these suppliers will almost certainly have what you need. Also, there is always the option to get spare parts for a particular bike. If you like the wheel set that comes with a a e.g. Specialized Langster and the shop do Specialized then you can ask them to quote you for a replacement wheelset. The same goes with Kona/Giant or whatever it is they do stock. With some brands these replacement parts are surprisingly competitively priced. Give the local shop a go even if they do need extra prodding and, if they are any good, they will give you service that the online box-shifters never can.