I have most of the pussy pumps and Doc Johnsons Pussy pumps is the best, but it covers the whole pussy. It gives the best seal on your pussy as it will fit most girls.
I have this one too but found it was way too big for me, I couldnt get a good seal without sitting up.
http://www.lovehoney.co.uk/product.cfm?p=4784
If you have a pump already then I absolutely recomend the Cherry blossom clitoral stimulator, oh wow the best on the market, but it doesnt come with a pump.But as a clitoral vibrator its amazing the vibes are amazing, it comes with a jelly sleeve on the head with many soft fingers, so the suction from the pump pulls them ontop of your clit; then you turn on the vibes; (if you can handle anymore).
http://www.lovehoney.co.uk/product.cfm?p=17801
My review is underneath and I have more indepth photos on my review site; and explanation of which pumps will fit the cherry blossom; as sadly Doc johnsons pump wont fit.
http://midnight-boudoir.blogspot.com/2011/09/toy-joy-cherry-blossom-vibrating.html
I also have the nipple pump kit and that too does work as a clit pump but not as good as buying specifically.
Hope this helps.