Welcome to the community @Mink!
I’m not sure this relates only to child support, but that can be a place to start.
Many countries have bilateral agreements for enforcement of child support. Where are you from (resident/citizen), and where is he from (citizen and currently residing), if I may ask?
You could always try claiming the child support order in his country of citizenship. Some countries (including the US) may in some cases even cancel someone’s passport if they owe a significant amount of child support.
Leaving behind the child support issue, you could also sue him in your home country and try to get a ruling in your favor there. Depending on international agreements you might be able enforce it via his home country (where he’s a citizen) or other countries where he generally travels.
You could also go directly to his home country (where he’s a citizen) and file a lawsuit there. If he still has family there he’s likely to return there at some point, and his home government could give him troubles when he tries to renew his passport (in some cases at least).
I’m not sure how effective it would be, but you could also try filimg a suit where he does his banking.
Keep in mind, I’m no expert on this topic, so take my suggestions with a grain of salt. And you should really get some legal advice, as it sounds like a complex legal situation.