Off the top of my head:
CTMod
Telo's Mods
FlexBar
BibMod
All have customizable hotbars. I'm sure that there are many others too, but just doing a "straight off the top of my head", those ones immediately jumped to mind. Some of them (BibMod, FlexBar, Telo's SideBars) may or may not be included in some of the compliations available here, as well.
How they will behave with Cosmos, I can't say for sure.