Shopping list for the power steering overflow bottle mod:
Barb (4mm hose, M5 male thread)
http://www.ebay.com.au/itm/281878696727
Reservoir
http://www.ebay.com.au/itm/262315935885
Plastic 90 degree barb (perfect push fit into the hole in the cap)
http://www.ebay.com.au/itm/351042125127
Silicone hose
https://www.fcpeuro.com/products/bmw...er-11727545323
You'll have to come up with your own mount, could easily be done with a long M6 bolt with some nuts on it.