It doesn't look like you need the stanley kit to make the toddler bed in terms of stability since the photos of the conversion also show it with no rail at all. So I would just take off the front piece and use a universal toddler rail like this: http://www.amazon.com/KidCo-Converti.../dp/B002ZDFVP4
The conversion kit is expensive because it includes the pieces to make it a toddler bed and then to go into a full size bed, so it has the rails and mattress support parts that are more expensive. If you just want to do a toddler bed, I'd go the universal route.
M, mommy to A 2005, E 2007, and L 2010