Can I install a handlebar brake handle without removing the grips?
Many BMX levers are hinged, so they don't require messing with the grip. These can be had for either short pull (canti/caliper/u-brake) or long pull (v-brake/mechanical disc), so make sure to get the right pull. They're intended for one or two finger use.



Various basic "touring" levers, of the stamped sheet metal variety, also go on and off without removing the grip. Some, as in the currently made/available Sunlite one pictured below, have little clampy bits that detach and then are slid back into place, and others have a steel band clamp you can open up to bend around. These generally aren't the nicest brake levers, but they work and may match the aesthetic of the bike better.



FWIW, most nicer modern hydro levers have either a hinge, faceplate, or other scheme to allow this as well.