I noted that the Brompton pedals are made by Wellgo; so I got a pair of Wellgo dual sided clipless pedals that match the originals in looks, and just installed the right hand one. The left side is still the folding pedal; I have found that having just one clipless actually works much better than expected.

This is similar although mine has a natural frame, not black.

http://www.ebay.com.au/itm/Wellgo-C0...ht_2535wt_1139