Kensington 56146 Solemate Plus Adjustable Footrest, Gray
This has all the adjustable features you would want for a footrest.  The quality of the platic is great.    However, the rubber that your rest your feet on smell so bad that I'm sure whoever makes this footrest will have cancer.  I had to leave it in the garage for days before I could use it and I'm sure to not put my bare feet on it.  Lawyers, have at it.