You'll need to get a pair of thumb cuffs to start. I got them at a local toy store in the practical joke section for just over $1.
Then get a pair of jewelry pliers and detach the chain between the two cuffs. My cuffs are fully functional, so they can interlock and be my clasp.
So then just cut off a length of chain and attach it to the loops on the cuffs where the short chain was before.
Wear your jailbird fashion with pride ;)