Does anyone know of a canvas type top that can go underneath or above an AllPro bed rack?

I foolishly purchased that bed rack version that did not allow a soft topper to go underneath. I have dogs and take them on trips and I would like to have some shade for them in the bed.

Does any one know of a top, like a bikini style top or whatever that could be put over the bars? Or a something that could be suspended underneath?

 

Ive heard of people getting a custom canvas cover from places that make boat canopies but i havent heard of a company that stocks and sells one.

 

Buy a milltary quality tarp