Doesn't need to be Oberon, I bought a "factory racing" billet aluminium from ebay for £35.00 delivered. Someone on here posted a link (can't find it!) and a few of us purchased. Improvement over original for a 1/3 of the price for Oberon.
I'm not far from you in Glasgow, if you want to pop over for a pull of mine (no smart ass comments please
) then feel free..........