Ebay , seller's name is activeinkusa. It was about $6 for my HP printer with free shipping. Way less than HP, Walmart, or any ink website. I put one in last July and am still using it, and I print several sheets a day. Of course it is just Black, I don't have anything I need to print in color and I wouldn't spend the $$ on it.
I bought two, when the first one runs out I will order another, then I am never without one.
I wouldn't try refills, too much of a klutz and computer/printer are in the sewing room (eek!)