Is such a thing even possible?
There are plenty of websites where people are selling BTC for PP, but I'd bet most of them are either complete ripoffs or scams. 1) they are asking for 125-200% of current BTC values, 2) they advertise on the PTC sites where people are trying to 'earn' miniscule amounts of BTC for visiting websites, 3) the sites are very basic and probably thrown together in less than 10 minutes.
I'd sooner buy off of EBay than these sites, and I'd only buy there after making sure the transaction isn't somehow frowned upon by EBay. Having never bought BTC I have no recommendations where to go, but I'd look at the exchanges like BTCe or MtGox and see what payment processors they use if I were looking at buying.