Ask HN: Startup owes me money but keep delaying payment. What are my options?

I did work for a startup earlier this year. I got paid lower than my usual rate but with an agreement that I get some cash equity and deferred compensation upon raising money.

It's been more than 6 months since they raised funding but I have yet to be paid for my deferred compensation.

They are also in the process of being acquired. They offered to buy out my cash equity to just half. They said it would a pain having to include my options in the acquisition. I negotiated and we agreed for 80% of the value.

I was promised at least 4 times that they will be sending the payment but have missed them all.

I cannot take them seriously now and I fear that if this drag on longer I might not get paid especially if they close the acquisition.

The money they owe me is in the low 5 figures.

What are my options? Any idea how much it would cost me if I get lawyers involved?