Finding replacement upvc door keeps
It looks like you're measuring the screw distances correctly, centerline of screw to centerline of screw. If you can't find exactly what you want online, try hitting a few locksmith shops.
There is some tolerance in mounting these. Depending on the type, you can drill new holes or with a small round file, turn the existing holes into slotted holes. I have seen some that had no holes and you just drilled where you needed them to be.