We're having a hard time finding a co-sleeper (or, we'll happily take a guard-rail) that will fit / lock onto our bed which has a raised edge of 1"x1"...

We saw a crib at Mothercare with one of its sides slidable to convert into some sort of a co-sleeper. However, it doesn't have any device to latch onto the adult bed. Using it will also leave quite a gap between our mattress and the baby's mattress due to the 1" edge of our bed.

The raised edge of our bed is 1" high and 1" wide. Our mattress is 6" high. Has anyone seen a co-sleeper that will possibly latch onto our bed?