Well, if walking is a required option for your prisoner then forget these!  Dead easy to fit - none of the fiddling around with huge keys - these will clamp around you captive's ankles with one short sharp clunk.  Then there is no way they are coming undone without the tumbler lock keys.

The circumference of these little darlings is 8 1/2 inches or 22 cms.  To see whether they will fit just stretch a piece of string around the offender's ankle and measure!