Any Folder. Or none apart from the Brompton - depends. If there was an alternative that was light, as compact, as good and way cheaper - do you think Brompton would have sold more than 1/2 a million of their bikes? All cheaper alternatives differ in one way or another and only you can judge what is necessary or important to you and what would be a fair compromise for your needs (if there is one). If a new one is too expensive (which would be totally understandable) - why not look for a used one if a Brompton is what you want? Possibly better than spending what you have on a bike that you don't want and this way vaporizing the existing funding basis to get one. If you look at the bike as a way of transport you will probably discover that the Brompton is in no way expensive but saves more money than is costs relatively quickly compared to what you have to spend with alternative ways of transport. If that's not true for you maybe you don't need one but just want one (which again would be totally fair).