I remember discussing this with a breastfeeding coordinator in WIC
about a year ago and I was told that whenever a breastpump comes in
infested we must seal it with two heavy duty plastic bags and put the
pump under quarantine for three months.  I have never even thought
about using pesticides.  Another way that may work is a cloth
saturated with beer put next to the pump and in the morning kill all
the drunk roaches.  Then you could seal it with less carcasses in the
machine.

Good luck

Heidi Lunn, M.S., I.B.C.L.C.
Miami-Dade County WIC Breastfeeding
Program Administrator