There are several types of Surety (security) bonds..... another type is one that guarentees that you will pay all of your employees and subcontractors therefore freeing the customer from having any leins placed upon them if you were to fail to pay your help.
What I suggest is that you call for clarification to find out what type of bond this client is seeking you to actually have then call an insurance agent that deals with commercial/ businesss insurances and allow them to find the right fit for you.