chris- btw, for the front, since whiteline recommends using the same lock for their 25mm and 27mm, i just went with a 1" inner-diameter collar lock from ruland (as back up, im going to use the whiteline stock collars to start off).
check here for available sizes... i'd get the steel ones if you can. i got the aluminum pair cause amazon was out of stock.
Ruland MSP Two-Piece Clamping Shaft Collar, Metric: Amazon.com: Industrial & Scientific