Pat Egan of Khaki Corps Imports
http://www.khakicorpsimports.com/ they're in Tulsa Ok. If you own (or are going to own) a British MV you'll be dealing with them at some point. Good guy to deal with. Has all (or most of?) the ferret manuals you'll need as well as a lot of the smaller stuff. If & when you get the ferret, PM me and I'll try and dig up the other parts sources I have. Most are located in the UK.
I've owned two Mk.1/2s with the fixed cupola. They're nice vehicles. A friend local to me has one of the up armored Mk.2s (I forget it's proper designation) with the rotating turret.
Just some observations for you from a guy who's been inside a couple of ferrets:
The rotating turrets look cool because it's a "small wheeled tank" but unless your a rubbery 150lb 18 year old, they're kind of a PITA to get in & out of. I'm 5'11" and 200lbs and had no trouble getting in & out of the driver's position through the driver's hatch.
The turreted variants can seem a little top heavy while driving because of all that weight way up high. The Mk.1s ride like an over loaded car by comparison and being that much lighter, are kind of peppy (for an armored car)on road.
If it's a turreted model that you want, I'd skip the Mk.1 and hunt up one of those instead. Buying a Mk.1 and trying to convert it (especially on this side of the pond) is going to be expensive.
It's kind of funny in a way because originally the Mk.1/2 was my least favorite variant until I owned one. The fixed cupola is large & roomy and the vehicle itself is easier to get in & out of because of it. The cupola has a lockable hatch so the vehicle can be completely secured unlike a Mk.1.
Regards,
Matt