DSA is the only option I'm aware of for low height spherical caps.
What are you hoping to achieve with low height caps? No matter which type of keycap you use, the switch travel will be the same: 2mm to actuation, 4mm total. You could also look into SA profile caps, which are taller, but depending on the set's profile, could be all the same height (look for a set with all row three keycaps). I believe there are currently group buys running for both DSA sets and uniform row three SA sets.