AutoTopOff is a good choice. BRS has an inexpensive 1 also. Another option would be going to a A/C supply house and buying 1 or 2 floats for about $9 each. You can easily wire them in to an extension cord or the cord for the pump. You can also use a bucket an some soft airline with a knot in it to control the flow rate (only let it drip slowly) and work off of a syphon. This could be done for a couple bucks.