There are a few Aurelia saloons on the market at the moment, a B12, rally prepared, for £12K at Silchester Garage, (unless you want to go classic ralling I would steer clear!). There's a B10 for sale in Milan in blue at £15K euro which sounds reasonable on autoscout24, and another B10 coming up at the Coys Monaco auction, guide price £19 to £23K, or you could try Martin Willems in Holland who has his B21 on the market, you'll have to ask the price.
I would go for an early B10 over the later B12, but if you can find one, the B21 (B10 shape with 2litre engine) or even the B22 are the best bet. Happy hunting! Ade.