Low Cost RTK Solution, need module?

For those that have not read this:

http://gpspp.sakura.ne.jp/rtklib/rtklib.htm

They built an RTK corrected board for $400, which included the CPU and GPS module for 1-2cm GPS accuracy. Be sure to check this page:

http://gpspp.sakura.ne.jp/rtklib/rtklib_beagleboard.htm

I can’t seem to find the u-blox AEK-4T GPS module they used in their build. I am looking for a GPS module with external antenna that outputs raw measurement and satellite ephemeris output?

Anyone here with experience with their RTKLIB software? Any of the Sparkfun GPS modules work for this application?

Many thanks

Andy