Ok, I'm pretty sure those types of boots use a cylinder lock. check and see if the key hole is a regular slit or a circle.
If its a circle, heres what you do... Take a bic pen, the cheap kind with the plain plastic tube body. Take the point and ink out so you're just left with the tube. Cut slits in the end about 1/4 of an inch into the tube lengthways, 4 - 5 slits should be good. take your key and jam it in the cylinder lock and twist it around until you unlock the boot.
If it works on kryptonite bike locks it should work on that boot.