First question is it worth it ? I bought a 1 metre length of 16 x4mm pitch left hand leadscrew very cheaply.
It was enough to make three cross slide screws, I also bought 2 bronze nuts to suit. All for just over £50. I now have a new screw and nut fitted a spare screw and nut ready to fit and enough screw to make another left over. Google lead screw lots of suppliers, I used Automotion Components. Not sure if they do imperial sizes but others do. If the spare 16×4 LH is any use to you let me know.