Looking for a window part..!

Does anyone know where I can get one of these? Or even what I should be asking for?

It's a part from a metal internal secondary glazing unit. A sash type window that has this catch either side on a spring so that you can secure the window when you've moved it up or down in one of the holes in the frame.

I have lost the catch one side but have no idea where to get a new one or even what to ask for!!

Many thanks!