Which XT hub do you have? 6-bolt or centrelock rotor attachment
(they're quite different and need different tools to maintain)
What has actually happened to it? You say fallen apart,are the nuts loose on the axle? In which case they can easily be tightened with the right tools
Other hubs?
6-bolt XT is a 2004 groupset. So 430g ish weight, 16point freehub pickup speed, threaded 10mm axle w.QR
centrelock XT will be 2012, 2008 (M770 etc?) or if you look really hard they're probably some 2004 (M760 etc?) ones kicking about somewhere
2004 I should think will be similar to the 6bolt one
2008 is about 100g lighter than 2004, 36point freehub, oversize 14?mm axle (reducing to 10mm QR)
2009 SLX centrelock I think is about 380g. 32point pickup, 10mm threaded axle w.QR (CRC has some M500 series (16point) SLX hubs listed, they're not SLX
Also a 32point SLX freehub will bodge onto a 2004 6bolt XT hub IME
Similarish money
On-one has a 10mm thru-bolt hub for £40 IIRC (no idea on pickup speed) for about 300g
Superstar Switch EVO about £60. 24point pickup, 300gish weight, will convert to many different rear axle standards (QR, 10mm thru bolt, 12mm maxle, syntace 142mm)
Must be a few other things for similar money