well in the FAQ page they list the measurements - 3 by 6 by 2 wide mm
so after a few minutes of seaching ive come up with
http://www.bocabearings.com/cart/car...20&category=36
those are on sale - 4 dollars a piece (doesnt say shielded, shielded ones are not listed in the size stated - the gogo green seals are 4.50 a peice and are 2.5 mm wide
thats 56$ without shipping for the 3x6x2 and 63$ without shipping for the 3x6x2.5 sealed
or on towerhobbies duratrax lists a 3x6x2.3mm bearing for 3.99 for two - making it a 27$ without shipping kit
i wonder how close the tolerances have to be? and since most of my cars tolerances are off big time (wheels slide in and out etc) it may free up some play - i will mike my bearings when i get home and see how close they are to 2mm wide
wish i didnt buy the stock kit - but i do have two cars now (one is parts one is racer) so i might experiment
i wish my LHS had them