I don't know about the shielding you linked to, but i use a simple 300W external stepdown:
http://www.shadaloo.eu/index.php?route= ... h=stepdown
To use this on your cab, you will need to bypass the internal transformer.
Unplug the machine from the wall outlet and follow these steps:
(Failure to unplug the machine might result in shock and death, so yes, it must be unplugged!)
1. On the transformer, there are two wires plugged into the two lugs "8" - light blue and "9" - light pink.
These go from the transformer, into the power supply at the front.
The power supply needs AC 120, this is what the large transformer is supplying. (And it generates a magnetic field while doing so.)
-> Wiggle off the two connectors 8 and 9 from the large transformer.
2. In your pic of the 'back power area' the wall cable is at the bottom. As you can see, brown and blue go into the bottom, yellow/green ground is screwed into the plate.
From that transparant fuse block, the incoming power is wired to a switch and then enters the line filter at the bottom. In your pic, a black sleeved cable with tie wrap is seen.
The black sleeved cable goes to the transformer, supplying it with 240 AC.
-> Disconnect the top left blue wire, and disconnect the top left brown wire.
3. The light blue "8" wire that we disconnected from the large transformer goes on the top left terminal of the line filter.
4. The light pink "9" wire that we disconnected from the large transformer goes to the top right terminal of the line filter.
You might need to purchase two proper terminal connectors (spade type) of the ones in place (see
http://www.shadaloo.eu/index.php?route= ... uct_id=157)
From this point on: The cab is wired for 120AC, and you do not plug it into the UK wall outlet ever! 
Stepdown i linked to is external, sits besides the cab. Takes UK AC power from the wall, and delivers 120AC into the cab.
You might need to purchase a US type 2-pronged flat power plug to stick into the stepdown, not sure if the power plug is the same.
I think your astro->wall plug might be replaced with a power plug type that unscrews, they probably cut off the original which is molded type and does not come off. (At least it is molded type on my Astro.)
The end result will still have the transformer sitting inside the cab, but it's not doing anything so there's no magnetic field
You could remove it and sell the copper to some recycling company. €4.50/Kg today. I would guess a bigass transformer ~5-10 Kg, check with yer local scrap yard
I'll send you a PM.