Although Dubro (I think it's Dubro) makes a less expensive one than this
http://www3.towerhobbies.com/cgi-bin...&I=LXXF25&P=ML
I use this sort of thing for two reasons: to reduce or prevent foaming in the fuel tank and to act as a filter, if I realy need one. It's there and works fine.
I found the Dubro one.. here it is:
http://www3.towerhobbies.com/cgi-bin...?&I=LXD741&P=7
CGr.