As you have found out there only seems to be one true steering damper currently on the market, and it's a speciality product for downhill MTB racing or dealing with cross winds on time trial bikes. This is not a product for the problem you are experiencing - losing control when the front wheel hits a bump.
It actually sounds like you have balance and stability problems, I doubt a steering damper would actually help you and would even hinder you as it would resist steering inputs from the handlebars as well as forces on the front wheel.
A possible way forward for you would be to learn how to deal with road irregularities better - taking weight off saddle and onto pedals through legs, shifting weight backwards, avoiding potholes entirely.