Have you looking into the Finnex ones?
Or how much do you want to spend?
-Sent from my Samsung Note, a "Phablet"
Finnex ones are pretty good. I think they have a separate temperature controller you can buy as well. I just hate having equipment in the tank itself unless it's glassware, so I'm a bit biased when I say look into the Hydor ETH in-line heaters.