I have several ideas for you,
You can try looking on the free section of your local craigslist to see if anyone is giving away any of that type.
Depending on how much you're willing to pay, Woodcraft, a woodworking store sells high quality softwoods that you can buy. But its probably going to be expensive. Very expensive.
&*& - Check out this link for some great info to know about this wood before you start working with it.
http://www.woodworkerssource.com/shop/category/pine_ponderosa.html