Victoria and Czar are both self fertile plums. Many suppliers offer dwarf family trees that have two or three compatible varieties grafted onto the same trunk. That way you only need one tree as the varieties pollinate each other. Check the Ken Muir web site for available trees (new season stock, not yet listed). I have bought a dozen or so trees from him and can vouch for the quality. If you are able to visit his nursery, there are some great bargains to be had, most of my trees cost me £10.
At the end of the season, any bare root trees not sold are potted and sold cheaply in containers. My problem is that every tine we go, another tree or two finds its way into the car. Their nursery is near Clacton, North Essex.