I have used in the past a sherpa V8 master cyl with remote reservoir, and slave cyl from same, but the BMW E36 slave can be used and is a good fit around £15 new from the bay on a good week, just get a master with similar or slightly more bore diametre, so long as the push on the master is enough for the stroke of the slave it will work, you can also set your biting point where you like, the bit of metal re-inforcement that IS needed can be made easy enough, with some 3mm sheet mild steel, then measure and get pipe made to suit.
I did a conversion on my dads xr4i around 7-8 years ago, and apart from having to renew the master cyl seals once has been faultless.
This is without doubt the best thing mod wise you can do to a cossie, esp if uprated clutch, the clutch will become so light and easy but totally progressive so really good for any snatchy clutches, mines a bit like that and with the cable sticking etc as it wears through the nylon inner and starts jamming up it can be a bit awkward, but love it when I need to use the 4i with hydraulic!!
tabetha