I'm not sure about this, but I think perhaps trailers having partly enclosed propane storage areas (bottom of compartment always left open for safety since propane is heavier than air) are intentionally designed without locks in order to permit very quick access in case of emergency. Just something you might want to consider.
Our last trailer - an " Award" was designed so that the bottles were completely hidden within the trailer profile, although the fibreglass access door had catches without locks - the only compartment on the trailer so fitted.
When I questioned the lack of keylocks, that was what I was told.
Brian & Connie Mitchell
2005 Classic 30'
Hensley Arrow / Centramatics
2008 GMC Sierra SLT 2500HD,4x4,Crew Cab, Diesel, Leer cap.