How do you find sponsors?

I recently launched https://uicoach.io and got some good results: 37,000 website views 14,000 active users 227,000 engagement events But the challenge I'm facing now is finding a sponsor to pay for the server cost of the upcoming features, the profit model I used didn't really work. I haven't done this before so I have no idea how to find and approach sponsors so I was wondering if anyone here can give me some advice.