Tropical Marine Centre recently launched its V2Auto Top Up as a low voltage automatic top off system geared towards being and affordable option for hobbyists. Like other top off systems (or top up, depending on which side of the pond you are on), the V2Auto Top Up uses float switches and a 3.5 watt 12V DC pump that can deliver up to 200 lph (around 60 US gallons) with a max head of 2m.
There are two different V2Auto Top Up systems available: a standard with one float switch that retails for £39.99 (approx. $62 USD) and the Plus system with two float switches for added redundancy and protection from overfilling the system for £59.99 (approx. $93 USD). No word on availability of this on the North American side and how in line the pricing will be.