Drill the head of the bolts (they're mild steel so should be easy), get some 0.032" Stainless steel lockwire, a pair of lockwire pliers and lockwire them up a la aircraft style.
Sounds like that's the only way you'll solve your issue.
If you were in Adelaide, I'd even show you how to do it properly. 99% of people have no idea on how to do it so that it actually works