Well, I'll just have to keep telling myself the $150 "added value" was that I couldn't find anybody that had them in stock ... otherwise I might just start crying that I burned my drinking money.
Other than many BMW dealers (on-site OR on-line) AND BeemerBoneyard, there is a good supplier based in UK called MOTO-BINS. They have been in business for a long time selling BMW specific parts and are well known in UK and Europe. I have ordered from them 3 times - they are reliable, have very good prices and ship fairly quickly at a very acceptable price to North-America (in my case CANADA). Often the shipping charge were equivalent or even lower than ordering from USA (for me anyway).
They always had good prices, but even more so since the UK pound has lost some value. It varied from 1.7 in 2014 to 1.2 in 2017. Now sitting at approx 1.4 compare to $US$.
Currently on MOTO-BINS web site, they have these 4 choices. Because the last 2 choices are unknown to me, I would choose item 1 or 2. I have never seen any feedback from item 3 below and surely it is not Siebenrock based on picture:
1) The original BMW friction plate (21 21 7 670 455): at 78.5 UK pound (roughly $US$ 110)
2) a 3rd party "heat resistant" friction plate - based on picture, it looks like Siebenrock: at 75 UK pound (roughly $US$ 105)
3) a 3rd party oil-resistant plate (I have never seen this one... kevlar??): at 85 UK pound (roughly $US$ 119)
4) a "cheap" 3rd party regular friction plate: at 44 UK pound (roughly $US$ 62)
To avoid searching, enter with this link for all K1200 "brick-engine" parts they sell:
THEN select CLUTCH,
THEN select all 4 items from the 2nd row column on right to see all Clutch friction Plate available.
DISREGUARD the VAT tax numbers as the price charges to mail-order customer outside UK is the value "ex VAT"
WHEN you get to the end (shipping cart), pay attention to shipping COUNTRY and the choices of shipping offered: