What material are you milling?

My advice is get one of the "mixed" sets:

.6-1.5: http://www.amazon.com/LSD-Tungsten-Carbide-Circuit-Endmills/dp/B012V9HP2S/ref=sr_1_9?ie=UTF8&qid=1447446455&sr=8-9&keywords=.5mm+endmill

Dunno if the extra .1mm is important, but sure you can more .5mm endmills:

http://www.amazon.com/Tungsten-Carbide-EndMill-Milling-Cutters/dp/B00SXCK44E/ref=sr_1_1?ie=UTF8&qid=1447446455&sr=8-1&keywords=.5mm+endmill&pebp=1447446457660&perid=1KPPA2SBTSVDYDQJ10QQ