Hmm, I know you can get 4 string capo's and the like, but I'm not sure about single string.
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I don't think so man...not for a single string. I use capo on the E and B strings for some really weird tunings on acoustic....but one string would be tough.
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That's the closest thing that I could find but it seems like it would just get in the way if you were only using it for one string.
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transpose the songs so that you can play them in drop d. or tune back up a whole step. the difference isn't so huge that you'll really need to set up your guitar again. unless you've got a floyd. then...um...d-tuna?
Well I'm no expert but
You could just get a capo and tune your guitar to D standard, and put the capo on the 2nd fret to get standard tuning, and if you wanna play drop D just remove the low E string from under the capo.
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