where I can purchase the above Alenco cam lock.
Alenco cam lock
Hello,
I would recommend starting by comparing the specifications of the 90-025 window lock with 7/8" hole spacing to yours. See the 90-020 for the opposite-handed version. We also offer two keepers commonly used with this lock, the 90-108 and 90-110. Take a look and compare the specifications of these parts to your original lock assembly. Thank you!
onto the face of the fixed window below and protrudes upward to receive the cam.
I can't be sure with your keeper still installed but take a look and see if the 90-273 Alenco keeper might be what you need.
The 90-273 keeper is actually riveted to the frame at the factory. These aren't easy to replace since the manufacturer never intended you to repair them in any way.
Ideally, you can raise the bottom sash and then lower the top sash to access the old keeper. Pull it off to expose the two holes for the pins on the back of the keeper to slide in and see if you can somehow crimp the pins from the outside of the sash frame.
I want to stress that this is not easy. I am sorry that there is no simpler solution.