Is it Difficult to find a Cell Phone/GPS Jammer?

Jam Session: More Text on Texting

…I came across the usual comment made in such articles that The law notwithstanding, these gizmos are widely available on the Internet. Cohen’s article points to a URL name that looks like it is an online store for phone jamming equipment. But, it didn’t have anything directly available for purchase and looked more like a spam-link site than anything else to me.

So, how hard is it to find a legitmate source of phone and GPS jamming equipment in the U.S.?