I do not have a complete circuit to share, but I do understand the problem.
PoE switches periodically present a test voltage, and expect to see a 24.9k signature resistor. So you're good on that front.
Then the switch will to see the PD present a low resistance to set the class (maximum power). I think the lowest possible class is approx 1800 ohms.
What that means is you need some sort of state machine to present the right resistance at the right time. The switch is prohibited from powering a purely passive load, so putting 1800 || 24.9k won't work.
I think the PoE PD chips are worth the cost. There are quite a few ways to mess up standards-compliant PoE, but the chips protect you from many of them.