I do not recall Alenco ever using a single hole lock. SWISCO does carry some single hole locks, take a look at 90-026
. However, Alenco changed over to a sweep lock 90-005
. That might possible work for you but it will need new installation holes to attach. If you do go with the 90-005 make sure you do not break the glass with the new installation holes and always wear safety goggles when you do any drilling. You might want to consult a window mechanic to do the work.