Thought I'd post this in case there are any self-bondage Deviants out there who haven't discovered it.  These locks can be ordered from Amazon.  I found 2 for $39 and the cheapest to buy 1 is $25.  Time can be set to maximum of 99 hrs 59 mins.  Be careful, there is NO key and when the time is set and the lock closed, after a 5 second countdown, the time is activated and the lock will NOT open until the time runs out.

(In case you're wondering about the carabiner style connector in the picture, when there is tension on it, it's impossible for unlatch with the hand in the cuff and very hard even if the other hand is free. It is connected to a rope ratchet, Amazon or even Home Depot, as cheap as $6 a pair for the 1/8 in rope model)