I had a relatively inexpensive breast pump that worked quite well. It did apply quite a bit of suction, but had a hole that you used a finger to cover to make it cycle between suction and no suction to give a pumping sensation. It did provide some good nipple stimulation, but if you are looking for something to enlarge them, this ain't it.
One thing that I've seen, but not tried, since they sre quite expensive,is an automatic "double pumper" that works on both breasts at the same time, and cycles the pumping action automatically. If you've ever seen a milking machine for dairy cows, the principle is the same. There are also special "bra's" available that allow the pump to be used hands free. These are also rather expensive. I think it would be real interesting to be using one of the double pumpers, combined with the special bra hands free while sitting at the computer or maybe while watching TV or doing something else.
If the cost doesn't scare you off, do a Google search for "breast pumps" or "maternity supplies". Figure $200-250 for a decent pump and $50 or so for the special bra.