Have an actor dress up as a police officer or detective (if male, a fedora is required) and visit the HR department of your target employer. Don’t know who’s in charge? The “officers” can merely ask the receptionist. A toy “crime fighter” badge flashed quickly is usually enough to get the names out. The “detectives” can then ask to be escorted to the relevant office–no security required!
If a pesky, nosy receptionist asks your “policemen” to identify their agency, their response should be, “some people say DRY ICE” followed up with an immediate chuckle. Note that this is not a lie–some people do say “dry ice.” They never claimed to have a relationship with Homeland Security. If you really want to have fun, pay SAG/AFTRA union rates for their time. This lets them be accompanied by a film crew, which attracts attention but that’s not necessarily a bad thing.
Another relatively inexpensive option is to hire a private process server. These individuals don’t care what documents they are delivering and magically know how to open doors and insist on face to face meet-ups with their (HR) target.
Every time you see an ad, ask yourself if that bit of marketing could help you get hired.