Insurance to cover the contents of my trailer.

Well as some may have seen, I am looking into purchasing an enclosed trailer. My main reason for doing this is to help a buddy out and make some $$$ while doing so. My problem now is finding insurance! I am thinking on starting a new LLC and insuring the truck and trailer through that. Ok no problem but every insurance agent I have spoken with says that won't cover the contents of the trailer! That is my biggest concern!!! I am going to be having 2 cars in there a trip valued at a total of about $65,000 so I was gonna say to be safe get cargo insurance of $100,000. Just seems nobody can do it and most don't even know how to even quote it. Can anyone help me out here>??? Is there a technical name that I don't know for it>??? Any idea on a round-about cost figure>??? I am 23 with a pretty clean record(1 ticket in last 5 years). Truck would be my 06 Dually, trailer would be a 07' Haulmark 32' enclosed. I don't want to purchase the trailer then be stuck. He already needs 3 cars moved in 2 weeks and I am cutting it down to the wire and would like to get those hauls. Thanks, -Mat-