Insurance for my rental condo in Boston, MA

[Paul B.]

I own a 1 BR condo in Boston. The condo association has a master policy for the building. My tenant (hopefully) has renters insurance for his personal property. I have renters insurance because I rent my primary residence in Texas. 

A few years ago, I had a water leak in my unit, and I was responsible for replacing my neighbor's ceiling below me. That's when I realized I had an insurance gap, not only for that situation but for any damage within my own unit, such as a fire. So I called my car insurer (GEICO) and explained the situation. I ended up with a policy through Stillwater that is about $400/year. 

I have no idea whether that is a good rate, and if I am even properly covered. Should I be looking for an investor-friendly insurance broker, who understands the local market (my car and apartment are insured in Texas, while my investment is in Massachusetts)? Or is this a fairly common scenario? I don't want gaps or overlaps in my coverage. 

Can anyone recommend someone in the Boston area who insures rental property?