My wife is pretty talented with a needle and custom fabricated a shower curtain to fit the curve of the trailer. The curtain covers the door, and the toilet area. We bought the track from the above mentioned curtain tracks and stuck it to the fiberglass with Velcro. The track came with slides imbedded into a groove and I attached the shower curtain to the slides with zip ties. We had showers in the Ollie for the first time this Summer and the curtain works great.
I would send some pics but the area is so confined I CAN't get a good angle.
As far as the price, I agree...they have become rather spendy, but you can buy the base trailer for about $50,000 if you leave off some of the options. I imagine Oliver will keep raising prices until people stop ordering trailers.