Have you tried calling Grant Whipp; Lil Bear in Redding, CA? That's where I got mine. I think you can ask for any length. 530-275-6728. Or web:
http://teardrops.net/lilbear/parts.html
Oh yeah, if you look at that web page, it says any size up to 8 feet. There you go!
BE SURE TO INSTALL THE HINGE FACING THE RIGHT WAY. There is a front & a back! The front side is the solid side. (I learned that the hard way!)
Also remember to ask for your hinge material to be a tiny bit longer than the width of your trailer. Then keep the front piece longer than the back (underside) piece. So when it does rain, the front piece sticks out and the water drops off, instead of running into the lower piece of the hinge tube. Mike S has a nice rainy day photo of that posted here somewhere. Search for "hurricane hinge" and you'll find it, and my tale of woe as I found out that mine was on backwards.
Oh & BTW, I saw that some people will shorten the back (lower) hinge piece even 1.5" more & then screw a screw into the top (front) hinge piece just a 1/2" from each edge. This will keep the top hinge (attached to the galley lid) from sliding left or right. I have a photo I can post if you need to see that.