Something like this? Depending on the rules for your train, you can just quick fold the rear under and strap it. When I ride Bart that's what I do; I don't bother to deal with the handlebars, although you can qr them and strap them along the top tube with the folding seat post.
Bike Friday Folding Bike 21 Speed ( Black ) | eBay And - since there's no folding hinge in the main tube, the ride is stiff and very much like a normal bike.