Not sure, but it appears Asiatam uses non threaded 3mm axles for the idlers? If so, I'd see if you could thread the tensioner for a 3mm bolt and use 3x6x2.5mm bearings instead of the size I used. Get a Socket head bolt long enough for the non threaded shoulder to go thru the bearings and cut the threads to length.
http://www.xheli.com/exi-br030625.html