I am in need of towing accessories for my car. Where can I get good ones??

Get an automatic puller. It's a device that you attach to an end of your trailer and if you want to pull something onto your trailer, you hook it up and it pulls it up.
Also, general 2x4's are usually good to keep everything stable. Even long boards to keep the material separate.
Straps are probably what you need most. Keep things stable.