I use a pump to make a Jamil style whirlpool. The chugger pumps run about 140.00 plus you will need some silicone hoses, valves, cam lock quick disconnects, etc... I'd budget 180.00 and you'd have a very well built whirlpool.
I have a friend that uses a motor mounted to the lid of his pot that turns a stainless fan blade like thing inside the liquid. It's completely custom built. I have no idea what it costs.
Both methods work really really really good.