All the under counter makers "I" have seen make 10 cups of coffee. There are just the two of us. We have a little bitty 4 cup drip coffee maker that stows away in the cabinet. We only paid about $15 for it.
Consider the option of not mounting the coffee maker and going with a regular one. With the limited space in the camper kitchen, it's nice to have it out of sight and mind when not it use. In our kitchen it would block a window or otherwise be in the way.
Of course our little maker only makes 4 cups and has no timer function. Your needs may vary!