I wanted a mount for my Nexus 7 tablet in my Kia Soul that could easily be stowed if I wasn't using the tablet and for security. I used part of a cheap tablet case for easy removal of the tablet and hot glued this 3D printed part that goes into the CD slot to the back of the case shell.
This should be compatible with any 'mini' sized tablet case...not sure how a bigger device would fair from a weight standpoint. You could likely also print any case that is a similar clip-in style and glue this part to it as well.
Note: I'm not responsible if this damages your cd player....it works in my car fine but yours may be different.

Start with a donor case for the tablet of your choice...you can get them at the dollar store cheap. It's the kind that has an inner plastic shell and usually a faux leather 'folio' style outer case. Remove the inner shell from the folio. Print the STL file and test the fit in your cd player. In my Kia, I had a small compartment above for sunglasses that flips up. I've used this mount with it closed fine but I also secured it by putting some velcro inside the lid that folds down and mates with the plastic shell holding it in place (see photo). I hot glued the printed part to the back of the shell.