The RM3 on The Reo site is my favorite, if you're willing to drill the air to your liking. It is an A6 dual coil that Rob converted to bottom feed.
The cyclone with AFC comes in bottom feed, it's in my top
three. The Loki Labs' Odin is also made in bottom feed. The classified here is one of the best places to find a variety of bottom feed atties.
Learning to drill out the center pin is not too difficult. Grab a couple of $8-$10 RDAs and go to it.
Another route, Fatdaddy vapes sells bottom feed center pins (hollow), but I do not know how well they perform.