I used a couple of pine bookshelf supports from HD. Painted them white and used white 100% silicone caulk to attach to keezer, held in place by several pieces of tape until cured. Then used 2" long strips of 3/4" wide stick-on Velcro to attach tray to supports. I used a staple gun on the ends of the cloth strips for the supports to help ensure they wouldn't pull up (I chose to use the loop side on the drip tray because I thought it would tolerate being washed better). Then attach the loop side to that and peel the backing. Make sure the bottom of the tray is clean (I used rubbing alcohol), carefully center it over supports and press down. Mine looks great and has worked perfectly for months and will support pitchers, glasses, etc. with no problems.
Cheers!