I would go to the bathroom section of either Home Depot or Lowe's and look at the wall hung cabinets that they have and see if you could find one to meet your needs and coordinate with your other cabinetry. I saw some that looked good and were maybe only 10-12 inches wide so that you wouldn't be bumping into it all the time after using the commode. May not match what you have exactly, but if you can get near to the color, I would think that would be easier than building your own. They would be able to help you with how to hang them also. We could use a little extra storage in our TT also, so want to thank you for giving me some ideas, also.