I'm looking through TRO:Prototypes and came across a few designs labeled SecurityMech.
First up is the PTN-2M Patron PatrolMech (pg.94-95), according to the fluff, it's aimed at the same market as the Copper.
Next is the SDT-1A Spindrift Aquatic SecurityMech (pg.98-99)
Followed by ARB-001 Arbiter SecurityMech (pg.100-101), I don't think this is what you're looking for but it has Security in the name so I threw it in.
I have a fetish for Blazers so this next one is in my strike zone. MN2-A Sarissa SecurityMech (pg.112-113) It's more a mech labeled as Security, but it has a Blazer so all is forgiven.
Honorable mention is the TBT-K7R Trebuchet (pg.114-115) it has a Taser(Battlemech) and a Chain Whip, it's dubbed the RepoMech in the fluff.
I hope it helps somewhat.