Need help: Longer cable for the SOL

[don.ald]

I have 3 sol units that I want to change. I have them over my 90g and don't really like the look. Sooooo.
I have three tanks and want to place one unit over each system and use the one controller.
Where can I get longer cables to connect the three units? The tanks are about 3 feet apart from one another.
I would prefer to shop online.
Thanks
Rick