Do a Google search on "Window Latch Replacements" and you might stumble across something. It would help if you knew a brand/manufacturer's name.

Pretty generic lock. Search Blaine window hardware. They will have one.

Windows on Washington is on it. Blaine Hardware are the go to guys for this any type of older window and door hardware.

You will need a measurement before you order it. Measure the center to center dimension on the two screws that hold it. Probably easier if you remove the broken lock.

If needed, it is also an XO slide. You look at the window from the outside and the "X" is the opening panel.

They have a small assortment at most Local hardware stores that should work.