Update: I managed to get one.
Looked on the internet and found the Company that makes the System in Germany. E Mailed them asking where I could get one from and they said their partner in the UK is Tinley Tech so I contacted them and although they don't have this particular one on their website they could supply one for £7.20 including Vat and P&P.
So as Simon suggested, Tinley Tech did have them but not listed on their website.
Probably also true for other BRC bits - they have only taken over very recently from the now defunct BRCGB who were the distributor prior to going bust.
Autogas2000 also have some bits in stock that aren't on the website, so can be worth phoning them too if your struggling for bits.