Another cheap thought.... I have a motion sensor in my garage with a alarm in the house (detached). My dad put his motion sensor in his van. If you could put a motion sensor in the car facing the bike and the alarm in the apartment you might be able to catch someone tampering with it. Same for a camera, put a motion camera in the car facing the bike.
https://www.homedepot.com/p/Safety-T...iABEgL4xfD_BwE