Ok, so you can pretty much use anything that has AM4 compatibility.

If you want another small AIO for example an Enermax Liqmax III or the Coolermaster ML120L (did not look up any quality tests, but they will do for a 3600). But you could also just get an air cooler like the be quiet Pure Rock Slim2 if your case has the space for one.

Edit: some coolers may need the standard AM4 cooler mounts that should have come with the motherboard, so check if you have those installed/lying around in a box, or if the cooler needs them, if you don't.