Zeropark is known for it's pop and domain redirect traffic, but they also sell push notification traffic with their self-serve platform.
Just like with pop and domain redirect campaigns, you can setup optimized Source and Target campaigns within Zeropark. So, once you have a RON campaign going and you see profitable Sources and Targets, you can setup a separate campaign targeting just those specific Sources and Targets.
You can also split test up to 10 different creatives on your campaigns!
Zeropark sells their push notification traffic on a CPC and have a minimum deposit of $200.
If you like Zeropark's push traffic, you may also want to check out their pop and domain redirect traffic