Don't quote me on this, but it would be my guess that any type of pump used for enlargement would only have a temporary affect. Maybe after extensive continual use you might see some lasting results, but then you also are running a risk of permanent tissue damage.
Good luck on your endeavor.
What she said...
It failed with penis pumps, where the tissue is sponge-like and has the elasticity to grow on it's own anyway... breast tissue is nothing alike, and the risk to damage is considerably higher, if you overdo it, to create bigger boobies.
And, what if I told you that it's more sick to live a masquerade life, hiding your nature, until old age turns you into a bitter, and sore caricature of your former self?