I ended up slightly modifying the slots on the featherboard, as well as designing new knobs and slides, all of which fit common-to-the-US 1/4-20 UNC hardware. Use lock nuts in the knobs and standard 2-inch-long hex bolts in the slides. The featherboard has slightly widened slots to accommodate the slightly-larger 1/4-inch bolts compared to 6mm bolts.
I've tested this setup in my DeWalt DWE7491RS table saw several times now, running 8/4 hard maple boards through it, and the featherboard works like a champ. Knobs could be a touch larger for easier grip and leverage when tightening or loosening, but overall work well and stay nice and tight with the lock nuts.
I've included larger-diameter versions of the knobs for anyone that would want to give them a try over the originals. I've also included Fusion 360 models for the knobs and slide in case anyone wants to make some further adjustments.
Edit: I'd suggest printing the featherboard model in PETG for flexibility and durability. I set my PLA version a little too tight against the fence for stability and snapped one or two of the fingers off.
Remixed from the featherboard design by Doug Joseph (@design8studio).
The author remixed this model.
Revision of the miter slot components to fit the DeWalt DWE7491RS table saw miter slots.