These aren't "official" Howard Stern items, but it might be fun to be Howard for Halloween. Howard Stern inspired costumes and wigs are available online.
Ronnie would also be a fun costume but then again, most people might not know who he is.
For those that don't remember, Howard Stern threw his hat in the ring as candidate for Governor of New York in 1994. Running on the Libertarian ticket, he actually generated a ton of press and was a serious factor in the election polls until eventually dropping out of the contest. Lots of great Stern political memorabilia out there.
For the obsessed HS fan, there are also a lot of “unusual” and random items out there..autographs, lighters, bumper stickers, you name it.
Howard Stern related stickers for your car or otherwise. Most are the Sirius show fist, but there are others available.