Missing plate

Thanks for posting! You may be able to use our 89-030 Multi-Point Striker, 89-036 Two-Point Adjustable Striker, or 89-042 Multi-Point Strike Plate (used along with the 89-043 Strike Plate Cover) to replace your keeper; although, I cannot make any guarantees they they will be a fit. These locks are made for compatibility with a mortise lock style different from yours but they may still be worth considering. 

Carefully review and compare each of their dimensions on the website to see if either of them could work for you.