It looks as though Mike James might sign with Mavs now, so time for plan B.
The only PF out there in free agency that could be had is Reggie Evans. But as others have mentioned, he has almost zero ability on offense. He can rebound the hell out of the ball though and gets under the oppositions skin. However, I remember JVG saying he couldn't stand his style of play last season.
Don't look for him in Houston. Other options: Darius Songaila, Melvin Ely (restricted, though), Othella Harrington, and Lorenzen Wright (can play PF).
And to touch on a point that SAKF made, Battier can guard 4s. Do you really think Juwan Howard could guard them better? That's how I look at it.