Is your 3v3 input a floating voltage, or is it off at less than 0.5v, and on at over 3v ?Is it a digital signal (on / off), or an analog signal ?
Is this just a level shifter, or is it a driver? What is it feeding into, an IC, or a load ?
Should be able to work the Philips recommended I2C level converter circuit this way.
It's very late here. I should revisit this tomorrow morning, with a fresh set of eyes.
I suppose a voltage divider to let the P-channel gate swing between 24V and 12V when the N-channel MOSFET was on would suffice.
@Runaway Pancake, I think you meant "Should be able to work. Philips recommended...", but I find this comparison a bit confusing.