I just want to add to Dan's post that Keh is also a potential source for these rare but much desirable lenses, although they have none for sale right now.
It is better to check foreign auction sites, as the Fuji MF cameras were rather popular in Europe, Australia and of course in Japan (Yahoo auctions for Japan). Don't forget that if you make a search from US eBay by selecting "Location: Worldwide", you won't get any hits from foreign eBay sites if you include the category (e.g. Cameras & Photo >Film Cameras > Medium Format > Other Medium Format), as foreign eBay sites will have different category names.
As usual on these auction sites, it is usually much cheaper to buy a whole lot including a camera body and some lenses than to buy individual lenses, even if you are interested in only one lens. As these cameras and lenses are very much in demand, it won't be difficult to resell the items you are not interested in. Last week, a Fujica G690 BL with a 65mm wide angle sold for $431.99, which is less than the price of the lens alone on Keh. The camera body will go for $300 at least if the buyer doesn't want to keep it.
Apart from the normal 3.5/100mm lens, the easiest lens to locate is the 8/65mm; then come the 5.6/180mm, the Auto-Exposure 3.5/100mm, the 5.6/65mm and the 5.6/150mm; the rarest of all being the superb 5.6/50mm superwide. Expect to pay $300 to $1000 per lens, depending on the condition and scarcity.
Cheers,
Sebastien