Cruzbike mtb cranks with the steel 24mm spindle and HT2 interface have worked well for me. I got these to try 155mm cranks, I have quite a few hard hours on these and have not had any issues.
I also got a set of cruzbike 140mm cranks from them just to try really short cranks - but with the 24mm aluminum spindle, and they have notable flex, even just on my commuter (they also don't have much clearance for wide chainstays). However they are advertised for kids/folding bikes, and would probably be fine in that application.