What action can I take when clients don’t pay their bills

I have a quick question about receiving payment from clients.  I work as a freelance tailor and seamstress in the fashion field and I’m having a difficult time with getting paid. Most of my work involves meeting clients at their house and fitting their clothing and then altering it at my studio.

I invoice them with net 30 days and sometimes they take 5 months if at all to pay. They seem to constantly feed me information about having it approved or it needs to have approval from a higher source, etc…. it’s debilitating for my business and I’m not sure how to collect my money.

The problem is the majority of them are very very famous actresses and celebrities and I’m not in a financial position to find legal representation to go up against them for only a couple of thousand dollars… is there some other means I can use to attain payment? It starts to become exhausting when I send 5 emails and I keep getting pushback.  I’ve looked into factoring as an option but that’s not really viable, and then someone suggested a collection agency.  I’m looking to see what other options maybe available for freelancers.