Hi Jack
Fantastic lathe but they have a wierd spindle thread, as you've probably found. I bought an Axminster Super precision chuck with a blank backplate and had a local engineering shop cut the right thread in for me. I took in the faceplate and they machined up a spindle to fit, then were able to cut the correct thread.
Problem is, I think I had one of the last SP chucks from Axminster and they are currently not available so it would be a case of getting whatever chuck you can with a blank back plate, or a backplate with a suitable size of metal that can be machined it suit.
I notice you are in Canada, I don't really know what's available to you over there but if you ask at your usual local supplier I'm sure they could point you in the right direction.
HTH
Richard