Just buy this It fit perfect. Swap pullies, Which a Auto Electrician shop can do. Cost me nothing last time I did it. Your problem solved.
Alternator Code Alt00255.
Comes of a land cruiser 90-04 1hz, 1hdt, 4.2ltr diesel
110 amp.
 
 

This is great news for anyone looking to change their altenator...and in my case i can report it works like charm.

92 Hard Top: that does sound like good option. I'm away at the moment so hard to look into it but I'll see if you can confirm this:

So the mounting bracket is the right size? & the pivot hole will take the mr2 adjustment bolt?

I understand the pulley will have to be changed but is the shaft diameter correct for MR2 pulley?

Is the B terminal (the thread that sticks out of the alternator from the regulator) the correct size for the mr2 fitting?

I see the LC unit has an oval plug, is that plug and play with the mr2 harness? (I have round plug obviously but have an oval plug adapter)

Thanks

MG_MR2
92 Hard Top: that does sound like good option. I'm away at the moment so hard to look into it but I'll see if you can confirm this:

So the mounting bracket is the right size? & the pivot hole will take the mr2 adjustment bolt?

I understand the pulley will have to be changed but is the shaft diameter correct for MR2 pulley?

Is the B terminal (the thread that sticks out of the alternator from the regulator) the correct size for the mr2 fitting?

I see the LC unit has an oval plug, is that plug and play with the mr2 harness? (I have round plug obviously but have an oval plug adapter)

Thanks

Yes they are, Auto  Electricians don't want you to know this. So they can charge you more. Because you Said JDM MR2.

Can one of you guys explain this in one post in a basic way as possible so numpties like me (who have alternator dramas) can understand what the solution is please?

In short:
 
The 100 amp alternators (predominantly JDM MR2s due to electric power steering) are notoriously difficult to find in Australia meaning when they fail your basically left with the only option being a reconditioned unit. Half the issue with that is reconditioning/rebuilding (particularly electrical) components is a dying trade.
 
The crux of this is what readily available alternator (from a different vehicle) will fit and work in an MR2.
 
Based on Xmr2 and 92 Hard Top it seems the Lancruiser alternator will work.
 
There's obviously a number of factors regarding an alternator fitting and working. Being the alternator is 110 amp is also obviously ideal (very close to the oem 100 amp).
 
The most obvious required change will be the pulley but as long as shaft diameters etc are the same its a matter of a rattle gun on the nut, pulling off pulley and putting on MR2 pulley, rattle gun on.
 
The other obvious issue is the plug but from what I can see the factory plug should work (or a simple adapter plug i.e. round plug to oval plug).
 
With all of that said, I'm leaning to picking one up to put all the above to the test, install it myself and test it. 

any alternator will work on any vehicle if it mounts up and pulley offset is correct,  you just gotta have the wiring correct. 
i've used alternators off v6 camry for the aw11 many times, now a 20v that has a different plug (squished oval type instead of round), i just used crimp connectors to give the 3 pins what they need to work.  
 
check that the main charge wire back to the pos battery post has continuity, the fuse able link could have blown.  i usually just replace the whole line with a good quality multistrand 8 gauge wire.
 
check that the plug with 3 pins is correct for the pins on the alt itself.  (most toyota's have the same plug to pin orientation though).  you can test those with a multimeter or test light.