Johnston, 19, achieved pop-culture notoriety when he fathered a child with Bristol Palin, the teenaged daughter of ex-Alaska governor and former Republican vice-presidential candidate Sarah Palin. He has been making public appearances and giving a variety of media interviews in recent weeks.
Bait & Tackle LLC, the parent company of amateur all-male website StraightCollegeMen.com has offered to pay Johnston $25,000 to perform a solo masturbation scene.
The offer was tendered in an open letter published on the microsite LeviNaked.com and signed by Bait & Tackle Owner Justin Clouse.
"Given your well-known heterosexuality, you likely don't know StraightCollegeMen.com and its hundreds of naked straight men, but we've been around for eight years," the letter reads in part.
Clouse touts 18 billboards around Las Vegas offering $500 to prospective male performers. "We're prepared to offer you 50 times the regular amount for a couple hours of your time," he said.
The site will also cover first-class airfare, accommodations and a limousine should Johnston accept the offer.
It is the second offer from an all-male adult company Johnston has fielded in a week.
Unzipped Media, parent company of adult magazine Unzipped, offered him a cover story and nude photo layout. His proposed compensation was not made public. At post time, Johnston had not responded to Unzipped Media’s proposition.
He prompted the offers following an appearance on the late-night talk show "Watch What Happens: Live!" on the Bravo cable network when he indicated that he would consider posing naked for the right amount of money.