The Nova is a very good option at the $ price but if you have shipped or buy from http://www.velochocolate.co.uk/ you're talking in the region of £400.

I'd give Fudge Cycles in Paddington London a ring on 0208 969 5991. They are very knowledgeable and helpful and technically very capable. I had my Brompton customised there and they did a greart job.