Hi, The best place to get Magura Spare Parts are Penton Parts USA.
Just Google to find the Web site.
They sould have the adjusters in stock. I have got Dark Grey ones off them before.
I think they were about $2.00 USD. I would buy a few for spares.
I also think they have Alloy ones but not Orange Plastic adjusters .
Also there is VMX Services Holland and Andre at Enduro Klassiker Austria.