Make one or have it made?

I have made my own from bedsheets, so they would come all the way to the floor. Easy to change out also depending on season. I use a grommet maker, but if you use a very thin sheet, it can be hard to tighten the grommet-fold the material over to create several layers! flannel sheets work really well.

Just buy regular cotton or other washable drapery panels, and use a vinyl liner behind them. You will still have to hem, but you will have such a wide range of choices!

The Fabric Workroom makes longer shower curtains. I thought about ordering some from them.

Here is a link that might be useful: fabric workroom