you should be able to take a two station fish tank areator from wal mart to achieve what you want,use the small hot water pvc pipe and make a neck to come across the top of your bucket,so a open end t on bottom to make it stand up and just a 90 out the top for the water to recycle from the bottom,i use a commercail grade pump in a 33 gal trash can and i have to leave about the top 6 inches of can empty just for the splatter and the head/foam to rise
I use a 300 ghp aquarium pump with 2 outlets/ 2 air stones, make usually 2 gal of tea then dilute it to 4. Worked pretty good from what I can tell..there are ways to calculate how much air/oxigen you need to inpout based on your tea volume but for my small needs I don't feel like I need to get so precise. With smaller batches of tea a couple of air stones work well. Sometimes it foams a lot sometimes it doesn't depending on the recipe I use...