Yea, I was looking for a solution a few weeks back. I was hopping to find a workable solution, something already "built"
I was unable. I had to build my own. Did not cost much, just an hassle building it. Oddly, I bought enough "stuff" to build 8 or 10 of them. It was easier to buy "bulk" in individual components.
Really its just a variable (user adjustable) power supply.