Chipbreaker mill, .156", .188" or 4mm

I slot aluminum on my 'hobby' WorkBee router (modified for extra rigidity). It's slow - I use a single flute HSS end mill in .025" passes to cut slots between .156" - .188" width, & usually no more than .188" deep. I'd like to try something different - a chipbreaker (rougher) end mill. They're not hard to find, but not in the size I need. I need something between .156" and .188" (or 4mm metric) cutting diameter. Does anybody know of a supplier that has something in this size that would be appropriate for aluminum?

Thanks..