Hardwerk,
To purchase insurance you really need to define the type of work you do. There are many types of insurance, Workers Comp & General liability are broad terms, depending on your spicific industry your coverages may very. For busniess insurance needs you really need to contact somebody like Willis, or Acordia. These are agents that purchase insurance through brokers, who then purchase it through underwirters (underwriters are the guys taking the actual risk). A large busniess insurance agency can put togeather a total package for you that may include Workers Comp GL, Umbrella, Bonding, bla bla bla...Like a lawyer you need to find an agent that you can develop a comfortable relationship with, these guys are not side thoughts but true partners that could make or break your busniess..
Since your question lacks any spicifics on what your doing, I really cant say much more...
Good luck with it..