http://www.pondking.com/product/pond-king-pro/ go to add ons, there is a picture of the battery mounted in under the deck.

You should be able to use any side post style bolt on inline cutoff switch that setup in the pictures. It'll bolt down to the threaded lug on the marine battery, then bolt down your + leads to the cut off switch threaded post. The switches are less than $10

Mat Peirce
1.25 acre southeast Iowa pond
LMB, BG, YP, WE, HSB, RES, BCP