I think you have a couple options here.
1, Take him to small claims court. They cannot make him pay though. The best outcome here would probably be a judgment against his company, if his company is profitable then this will cause him problems.
2, Sell the debt. There are loads of companies out there that will buy the debt. This may be the way to go if you have already given up on receiving any payment, at least you will get something and know he will be getting mithered constantly for payment. Some companies will chase for payment quite "aggressively" if that is what you wanted.
I hope you get this sorted whichever route you choose.