How Do You Find Sponsors for Microsites?

About a year ago I built an app called PrizeBox, which is an instant win giveaway WordPress plugin. While it is still most definitely in private beta, I've built a few microsites around the brand (such as The Survivor Box at thesurvivorbox DOT com ... IH rep won't let me link it) as real world use cases, but I'm at the point where I'm having trouble building long-term partnerships out of thin air.

The idea is that users are required to subscribe to open a PrizeBox, and subscribers are invited to open a box at regular intervals (e.g. once per day). If they don't win, they are often (but not always) invited to check out a related product at a discount.

The problem I have is that I want real long-term partners with really good discounts, but since I've had a hard time finding them, I'm relegated to using affiliate offers that, for the most part, SUCK.

My primary goal would be to align myself with Amazon sellers with closely matched product niches, and/or start a separate Amazon FBA business myself via Alibaba etc. The former is easiest, but the latter is long term preferred. However, all require mental energy, and I manage too many projects.

I do plan to release PrizeBox, privately, to select partners and build revenue based on a Monthly Active User pricing model. However, I don't see any reason to do so if I can become profitable managing my own network of microsites.

What would you recommend doing to find Amazon or other niche business owners interested in becoming long term sponsors or co-sponsors?