I remember Everest used to do them, but that was a long time ago and they only had like a 10c prize pool.
poker.com/carbon poker also had a similar thing, called fun step challenge. You have to play a 6 man sng and the winner get entry to step 2, which is also a 6 man sng with the winner again advancing to step 3. Step 3 was a 10 man sng and the winner got $1. I actually won one of those, lol.