Only ones i know of are power support and steinheil.
Im sure there are others, but the power support is generally regarded as the best one. They will be out later this month.
SGP Steinheil are the only ones I can think of that are in stock now, online only as far as I know though:
http://www.sgpstore.com/product_info.php/cPath/21_28_89/products_id/1461
There are also a bunch on eBay but who nows about the quality.
Oooo are the sgp ones considered good?