On my 2015 R3T the headlight is an H4, and the aux lights are H3 bulbs. Of course, I am making the assumption that our bikes are identical being only a year apart.
I just upgraded (?) the aux lights to LED. One of my Aux light bulbs burned out, and they are $15 each at the dealer. However I did go the in-expensive chinese route, and bought a brand off Amazon called Sunpie. Yup... But at $71 including shipping (CDN), so far I'm not disappointed, we'll see about their longevity. I did have to do a very simple cut and solder to the wires to get them to plug in, but overall they really aren't that bad. Their light output is different (light pattern) than the factory lights but the majority of my light output will be the LED headlight anyways (once I get that resolved) so I think these will fulfill their intended purpose as simply auxiliary lights. I can post a pic of them when I have a moment, they are on my phone.