Hi,
It's great that you are considering additional funding. The best way to find the right investor is to network in the fitness industry. Attend events that are relevant and where investors are likely to show up, such as Pitch competitions, startup events, investor dinners etc.
It's also important to choose the right investor - and not the first one that offers you money. Make sure you have at least 2-3 offers before you make a decision.
I hope it helps!
Sara