Just ordered a roll bar from Hard Dog. But I went the cheap route, so Im planning on having a buddy weld in some diagonals. But I have no idea where to buy tubing. The bar is made from 1.75 X .120 inch 1026 alloy, so thats what I would like.

 

I got mine from http://metalsdepot.com/products/hrsteel2.phtml?page=rndtube&LimAcc=$LimAcc

I did the same thing. I went cheap years ago and got an autopower bar but needed a diagonal for a track day. Just welded the diagonal in. Pretty easy and straight forward. That sized DOM tubing runs about $10 a foot. I wish I had taken pictures when I did it.