Threaten him with legal action first, before actually taking legal action, or even try using the tax department, (ie, you have an uncle in there) that would love to fully audit his business, before paying a lawyer your hard earned.

Fair trade and all that might be interested, and I take it you're not with the Union?

Or in the event you do use a lawyer, make sure his fees are covered on top of what is owed in your final payout , due to you having to use the lawyer to obtain what is rightfully yours in the first place.

Hope that helps.