Yes, I'm in a similar quandry. Too bad the RKs are out of production in 18". An E36 M3 pased through my hands a few years ago with a set of BBS RK 18x8.5 et38, which I think would fit the 1-Series. Wish I'd kept the wheels when I sold the car.
But check this
guy on bimmerforum.com selling forged BBS RS-GTs for $2K. Those are $3500 wheels and look to be in excellent condition. I almost went for them myself.