Way back when I was making my own machine I spent an age looking for suitable bellows and only came up with the exact same as Jonathan... In the end I went the origami route... made my own out of thick card that i scored to make the ridges, lots of folding and finally laminated them with that sticky plastic stuff you get in roles out of stationary shops. You get what you pay for I guess... but they are custom made made so are a nice fit and they do exactly what I need them too :)