What about Orwo films http://www.orwona.com/. Orwo 54 is 100 ISO and I know of someone who has settled on it as his replacement for Plus-x. I've not used it myself, but I do like the look of it http://www.flickr.com/search/?ss=2&w=all&q=orwo+UN54&m=text. it is only available in bulk, but the prices seems reasonable.

