Depending on what you're looking for, it may be just as easy to do it yourself.
A product like Conservators Wax (Lee Valley) or Renaissance Wax will clean up tarnished medals nicely without taking away too much of the patina. A product like AutoSol Metal Polish (Lee Valley) may be required for heavily tarnished or very dirty medals, but will certainly remove patina.
As mentioned, you may want to consider getting replacement medals/ribbons for display purposes - and then maintain the originals as heirlooms.
Easy enough to find a shadow box, and pins and mount them yourself. The mounting specifications are all available on the Veterans Affairs website.