To start with document EVERYTHING from day 1. Make sure you have a complete specifications document signed by both parties, this will make recovering your payment a lot easier should it go as far as small claims court.
A few solutions…. have a contracting stating that the website, content and anything to do with it are your property until payment is satisfactorily paid, do not release any of it. Small claims court. Otherwise, if you have a contract signed and full documentation, you can forward it to a debt recovery company. They will typically take 1/3 of the payment. Sounds expensive but think about it, you’ll be getting 2/3rds as opposed to 0. They will call the company and try to recover the debt for YEARS. It will also be reflected on their business credit rating.
Hope this helped!