I'm guessing you'll have to make one like I did for our Avion.
Pick a shower curtain you like, add these from Vintage Trailer Supply:
1960s Curtain Tabs
A heavy-duty sewing machine can poke the needle through those tabs and make a nice looking seam. I free-handed ours, looks OK and works well.
If you still have the old curtain you can use it as a a pattern. Otherwise you'll just have to make it fit.