The Wooly Mammoth is basically a slightly modified fuzzface, and it's basic sound is still that of a fuzzface, but with a bit more "pinch" to it.
And there are a million fuzzface clones out there. But of the ones I've demo'd the ones that come closest to that Wooly Mammoth "pinch" are:
1) Malekko Fuzz Omnicron Analog Fuzz
$130.00 -- comes really close.
2) Monsterpiece NPN -- pretty much nails the Mammoth thing; but actually a bit more versatile. $160
3) Kinda' pushing it at around $200, but the JHS 4-wheeler is another one that achieves the wm sound, and it's specifically designed for bass, which may or may not be an advantage.
Some real strong options there to consider either way -- even if they don't give you a perfect cop of the WM sound, these are all some excellent fuzz pedals that will work well for bass or 6-string.