The Bosch pt no. is 0192033004
Here is where I bought it.
http://www.ebay.com/itm/28v-Alternator- ... 1478485866?
It was pretty cheap at $45 AUD shipped or £10 if your in UK.
Note. This source isn't a genuine Bosch unit but on the box it came in it said... Brand is CARGO "Holger Christiansen- A Bosch group company" so its likely to be equal quality, maybe

I tried and tried to buy the said black plug but could not find the pattern anywhere, pity because if the reg is accidentally unplugged while engine running it stuffs it so mount it out of harms way!
Tantaka have the same part on their website catalogue but its listed/tranlates as a charge relay instead of charge regulator but its clearly the same part pictured. I would have bought it there but he didn't have PayPal that I could see and direct bank payments from here to overseas attract extra fees and higher conversion rates on our dollar.
Here's another link, same part different seller €16.95, this link has heaps of manufacture's pt no's.
http://www.lima-shop.de/en/product_info ... -1150.html
I hope this saves somebody the time it took me to research it.