Motorized electric pump (runs off 9V battery) for a Leak Sentinel leak detector. Retails at around USD 60-90 (depending on supplier):
http://www.divervision.com/seaandsea-electric-pump-for-leak-sentinel-46126.html
https://www.opticaloceansales.com/leak-sentinel-electric-vacuum-pump.html
Asking USD 40 + shipping