picked up a few of these off ebay
White Left Side Leather Motorcycle Solo Bag Swingarm Bag For Softail Bike Rk-208 | eBay
LongLifeLeather USA | eBay Stores
a few different colors to choose from. I got 3 already and they seem good enough for a bike. I'm a little miffed at the "last one" deal. you buy it and another pops up as the "last one". fooled me on that one, but I wanted them anyway.
since I change the seat stay/chain stay angle most times, these work good for me, but probably a little finagling would make them work on a regular bike if you liked it.
just letting y'all know.