This might work: http://www.digikey.com/product-detail/en/abracon-llc/AIRD-02-221K/535-11415-ND/2660709
7 Amps rating, 220 uH, through hole.
Note that the capacitors are important, too -- without the "H" of capacitors bracketing the inductor, you don't get the filter steepness you want.
And if 1000 uF is too big for you, 100 uF instead will raise the rejection frequency by little over 3x (sqrt(10)) -- if 800 Hz is still good for you, that'll work, too.
Thanks, I look forward to testing this. Good learning experience.
I'm going to check out one other thing this evening. To tell a bit more about the project, the 24V is for some "muscle wire" actuators controlled by the Teensy via mosfets. The rest of the system can run off a smaller 12V wall-wart transformer supply. But I think I probably need to share ground between the two in order for the mosfets to do their thing. It might be that I can share the ground only without getting the noise injected into the Teensy/capacitive circuits. Anyway I'll play with that tonight. If it works then all I need is a couple of $5. wall-wart adaptors, which I probably have a bucket full of somewhere