I have these clit pumping cylinders (link below), which can also be used on nipples. I have put a small length of Conductive Rubber tubing on/in one of them to simultaneously apply estim to it. Finally, a clit trode that doesn't fall off !!
I have an electric pump, but some of the hand pumps may be perfectly adequate, since you don't want or need very much of a pressure differential.
You can always apply a Hitachi Magic Wand to the outside of the cylinder, or on the mons, or against the labia. I sometimes apply it as a G-spot vibrator simultaneously. Women usually have the strongest orgasm of their lives this way.
However, I just bought a more slender Wand-like vibrator that can be inserted entirely into the vagina, and I think that might be even better to be used in combination.. I've only tried it once so far, but my Play Partner had a violent orgasm when it touched the vaginal opening and I never got it inserted. I think of it as a vibrating fisting device. I'm looking for someone on which to try this again. :-)