If you're not putting the player into the standard stereo spot, then the odds of finding a pre-made mounting kit will be slim. You will be on your own. Usually, they only make mounting kits for putting things into the standard stereo spot.

It is common for folks to drill holes in their docking sleds to match up with factory mounting points. This actually works quite well if it's done carefully. An example of such drilling can be found here.

I'm assuming the Kenwood CD is in the regular mounting spot right now? And no dash cutting was needed to install it? Well, if possible, I would recommend using the regular stereo mounting spot for the Rio Car and just removing the Kenwood CD altogether.