Actually 3.3 ohms is a little more than a 15% variation from a 3.9 ohm resistor.
A quick Google search shows that one of our sponsors, Parts Express, carries 1/2 & 1W flameproof and 5W wirewound 3.9 ohm resistors.
http://www.partsexpress.com/webpage....ID=3&x=11&y=11