The magazine is the September 1939 issue of Real Detective, with Lombard on the cover. (Is the yellow background to her head supposed to suggest moonlight, an angelic glow, or both?)
I recall reading about some sort of incident involving Carole, Clark and an unwanted visitor to their Encino ranch, but I'm not sure whether this was the one. The couple didn't move into the place for good until July, and with a September publication date, this magazine probably hit newsstands around mid-August at the latest.
Anyway, if you'd like to get this magazine, it's available at eBay -- but hurry. The auction ends a bit before 4:30 p.m. (Eastern) today. The starting bid is $24.99, and no one as yet has placed a bid. The site is at http://cgi.ebay.com/REAL-DETECTIVE-MAGAZINE-9-1939-CAROLE-LOMBARD-COVER_W0QQitemZ360119419227QQcmdZViewItemQQptZMagazines?hash=item360119419227&_trksid=p3286.c0.m14&_trkparms=66%3A2%7C65%3A1%7C39%3A1%7C240%3A1318.
Meanwhile, if someone has more information on the prowler incident I referred to, please let us know.