I'm looking for a sans-serif that has an extended tail on the "R", as seen in the attached image (which is the typeface Epic). I vaguely recall seeing this feature in a geometric sans somewhere, but my search hasn't been fruitful. Any help would be much appreciated!  

There should be quite a few typefaces. You can search on MyFonts for “swash sans”, “swash geometric” and so on. Make sure to also turn on the OpenType feature “swash” for the preview text. Then just scroll down and you  should find typefaces like this. 

https://www.myfonts.com/search/swash+sans/

Thanks Ralf, good tip!