Joined: Jul 2015
Posts: 7,361
Likes: 3,217
From: NW Oregon
Bikes: 1982 Trek 930R Custom, '91 Diamondback Ascent w/ XT, XTR updates, Fuji Team Pro CF road flyer, Specialized Sirrus Gravel Convert, '09 Comencal Meta 5.5 XC, '02 Marin MBX500, '84 Gitane Criterium bike
your only hope may be contacting the OEM for a new one.
i've never seen a fat bike with a 73mm BB shell..
the shells begin at 100mm width, and 120mm is also common.
i did see a 68 x 142, on ebay.... it might be made to kinda fit.... ?
ebay search: Bike Bicycle Bottom Bracket 68 x 142mm Square Taper
and there is an Origin8 that's not too spendy... it might work with spacers and a lock ring... ? you'd lose a half inch of shell contact, per side...
ebay search: ORIGIN8 XLT Square Taper BB 100mm x 164mm English JIS Steel Bottom Bracket
or go to a box store that stocks several fat tire bikes, measure a few BBs, and contact THAT MFG for a spare part....