I'm not quite sure I follow you there. If this is a custom part that you have designed, nobody on the internet is going to give you dimensions for it- you have to give them dimensions. You'll find dimensions for common stock items, like hexagonal bars, round tubing, etc, but if it's something you've dreamed up, you won't find anything on it.
You don't say what the material is. But you can get custom aluminum extrusions in just about any shape if you're willing to pay the die cost. I suppose you could get manufacturers to make this out of steel or other material, but you'd better need a bunch of it.
If it's a one-off item, you might consider forming it from strip or bar stock.