Rarely someone in the UK will sell one on social media but you need to be quick. Sometimes you have sellers in Asia but postage and tax, including tax on postage, will cost a bomb.
Respirit on here still sells some rep body parts and is probably the easiest option but doesn't have that particular bumper.
Yeah I've bought some bits of yahoo auctions. BHP imports got them for me. Issue is unless they are dirt cheap in the auction it's not worth it as tax and duty are pricey.
Problem is the Japanese market has seen a massive rise in prices too. E.g. a mugen wing could have been had for £1000 to your door a few years ago. You'll be looking at double that now