K-Mac make bars to order.
http://http://www.k-mac.com/
Pedders used to stock 140 bars, not sure if they still do.
Selby in Sydney used to make yellow 24mm bars, I had one of their examples years ago.
iPD sell and ship bars, but be prepared to spend.
I've heard that Whiteline bars are sand-filled tubes.
Standard bar is
21mm 17mm on my 74 145; you'll notice a real difference with a 24mm bar. You will however need to reinforce the link rod mounts on the lower wishbones, as the welds will crack.