Thanks a lot guys for the information, I really appreciated. I actually do have rental insurance which covers my equipment. It was a hard lesson to learn because my apartment got robbed. Thank god I didn't have my camera at the time!!
The problem is if the insurance company finds out the camera is used for commercial use, the quote overall will increase drastically. That's why am trying to find a company that I can just insure it for this trip only.
I get my all my camera gear insured for travel as part of my home insurance package. It allows me something like 60 days travel. I made sure they have a list of my gear and im insured for theft, loss and accidental damage etc. Even covered if i just leave it on a park bench and walk off. Off the top of my head it only works out at about 10 pounds a month extra. Stand alone polocirs are way more expensive.
I've always thought travel insurance for camera equipment was too expensive but that was a long time ago (15 years ago). I guess that if you have a lot of really expensive stuff, you might want to consider it nevertheless. You'd want to check carefully which exclusions are put into the contract, it wouldn't be very nice to pay for an insurance only to find out they won't pay you after your stuff got damaged doing some kind of adventurous activity.
No idea about which US insurance company offers good rates, sorry.