I found the metal ones at these sources but I know nothing about the retailers:
http://store.quiltworx.com/product-p/cebb3.htm
http://scarlettrose.com/set_of_7_bias_bars.html
hope that helps you in finding what you want.
Even though I've never used these in making bias strips, they look very interesting, so much so that it's worth my time exploring their use.