Finding an adapter plate can be difficult because lots of vendors have their own specs to boost their selling. You have to measure the spindle pretty accurate to predict an adapter plate will fit. As an alternative, you could make (drill and turn) your adapter plate. If you don't change the chuck very often (like me) making out of (a thick piece) aluminum will do fine. An adapter plate, made on the lathe it is used for, will run absolutely true. I have made several aluminum adapter plates for my mini lathe and even after 10 years the still are in mint condition.
If you make the fit for the chuck with a bit of play, you can use this play to reduce the runout of the chuck. I have done this on all my adapter plates, even those that came with my bigger lathe.