I do a lot of bike fit for women. I've been shimming levers for years (before Shimano came out with their fancy shims). I use those little felt/wool carpet squares that you put under furniture that goes on wood floors (I'm sure they have a real name but I can't think of it). They're felt on one side and adhesive on the other. Just depress the lever and insert the shim on the solid part of the lever (inside). You may need to adjust your brakes after doing this if they're running too close to your rims. This, of course, only works on Shimano. I haven't figured out how to do this for Campy, but I understand that there's a shop in Santa Cruz, CA that fabricates custom Campy shims.