The one you linked uses two well-regarded TPA3116D2 chips, one for the stereo channels and one for the sub. If you only want the sub amp out of it, here is a product with just that part: https://www.amazon.com/AOSHIKE-Subwoofer-Amplifier-amplifier-Accessories/dp/B01N5DGK37/ Use any old 19v laptop charger to power it, to keep it as cheap as possible. Though you lose a little power compared to buying a 24v supply (5-6amps).

Approx clean power ratings from the datasheet. These are clean, real RMS watts (not peak), at 1% distortion (not 10%). Though fwiw, the tiny little heatsink won't let it put out full power for long):
19v: 55w@3Ohm, 42w@4ohm
24v: 95w@3ohm, 72w@4ohm

I wouldn't be at all surprised if it was more than enough power for your projects.