I lost one of the aluminium feet from my DIY mechanical keyboard. Rather than order more, I simply measured the existing one, modelled it up and printed my own. There is a small gap in the top where you can add a small silicone furniture foot (or a blob of hotglue!) for some extra grip. 

I designed these for my keyboards and macropads but you can use them for all kinds of things (for example, they could be great for lifting a laptop off the desk and improving cooling!)

Printing:

I doubt these need to be terribly strong, but since they are so small I just printed them with 100% infill.