I was looking at HSS, my understanding is that carbide is unnecessary and possibly undesirable for non-ferrous metals, although that second part seems to be debatable depending on who you ask.
I did find a few by searching 3/64, 1/16, 3/32 end mill, but very mixed results. Also I see I left it out but I'm hoping to find them with a 3/16" shank to fit my smallest collet. That last is not a deal breaker, just means I'll need to get a smaller collet. I thought perhaps I was using the wrong term for what I need.
Intended materials aluminum, or brass
It would be used in a Sherline 5400 mill
The immediate project would be making wheel hubs for a 1/25 scale truck, so making several short (perhaps 1/4"), shallow length ways slots on 1/4-3/8" rod. I haven't figured out how to post photos since photobucket went insane, but I'm sure everybody has seen a truck hub with the rise and fall around the body of the hub.
If there are other options for tools I'm all ears. I was also considering Dremel bits if I could find the right size / shape. This would also require a smaller collet since they have 1/8" shanks.