PSI has one - they are in Philadelphia. They also have a stopper mandrel that is less expensive than their Jacobs chuck. My preference would be the mandrel - a Jacobs chuck is great, but you would also need a drawrod (you can make your own using 1/4"x20 allthread, a nut and a block of wood) to hold the taper into the spindle of your lathe. Also, the arbor on the PSI Jacobs chuck has a J33 taper that holds the chuck itself on the arbor, so you would need to use your tailstock to keep pressure on the workpiece to assure that the chuck remains in place. The mandrel threads onto the spindle, and while you would probably want to use your tailstock to put some pressure on the blank while you initially turn it down to a cylinder, you don't need to be as concerned about the workpiece coming loose if your turning puts lateral force on the workpiece.
Do you have a faceplate? If so, you can always make a chuck. Bore a hole in a piece of waste wood that is large enough for a 3/8" bolt. You will need some screws to attach the waste block to the face plate, and a 3/8"x16 bolt that is long enough to go through the waste block and 1/2 - 3/4" into the stopper blank.If your faceplate has a center hole, simply run the bolt through the hole, and screw it into the bottom of the stopper blank. If your faceplate doesn't have a center hole, you will need to bore a hole to receive the head of the bolt - that hole doesn't need to be precise, so a spade bit would be fine if you don't have a forstner bit.
