I've been on the look out for decent bridges for Warmaster but generally found them to be too wide/long or to have so much "stuff" at the bottom of them that they would look awful when put on your own river scenery.
Lord knows I'm not going to ever get hold of a FW bridge for a good price so I've occasionally rooted around different terrain sites. I keep going back to Leven now and then even though it is "downscale" from the point of view of cost but also the high quality of their sculpts.
Just realised they've put up some bridges:
http://www.levenminiatures.co.uk/bridges.htmNow, these aren't quite 20mm wide so that will look awkward shuffling stands across, but there's no stuff on the bottom and they aren't too long. I'm planning on 3 inch wide rivers so this would suit me rather well.