Cut Capo for open tuning?

Hey,

Looking for a capo that covers 2-3-4, so if it's on the 2nd fret I get a'd'f#'a' ("Open D", "Machete D", etc).

Does anyone make that?

If I have to mod my own, what things to I need to watch out for when modding? Does it need an "outrigger" touching the fingerboard beyond the 1st string, or will the three strings give enough support and not torque things out of intonation?

Thanks!

As Ubulele says, you can use some regular capos. I took a D'Adderio capo off my banjo for this photo. It works just fine, but as Ubulele said, if you barre at the 4th fret, you still get an E6 chord. The capo only affects the unfretted strings. once you fret it, you're back to standard tuning, so it won't work for slide playing.
To get a true open D, you'll have to either tune the bottom three strings up a tone or drop the top string from A to G and put the capo on the 2nd fret.