Alternatively, you could try an SM58 pretty close in. It does have a tinny sort of sound {the banjo and bouzouki carry a fatter sort of sound} but I've found the thin~ness only tends to be on the E and A strings as they're the thinner ones.
I record mandolin quite a bit but I don't use the instrument conventionally {for example, electric mandolin is like a super raw punky guitar in the wrong hands ~ mine}. I bought mine 2nd hand 20 years ago (I was in my 'Celtic folk and Horslips' phase) and it had a contact mic on it. I've found amplifying it very useful, not only for the raw sound, but also to add a slight edge and lift to it's natural sound.