I have the Saddlemen TS3200. I paid about 85 bucks for it.
Pluses +
It wraps over the passenger seat so you have deeper side pockets like saddlebags. And exterior zip pockets for misc. stuff. It's great for a carrying a TON of stuff. Like for a long weekend trip. I can even fit an LL Bean 2 person dome tent in it along with other gear.
It's very stable on the bike provided you paid attention to the connections you devise (tightness, connection points, and some common sense). You forget it's there.
Plus it's also a duffle bag with a top handle and shoulder strap. You just unsnap it from the bike and leave the attachment straps in place. So you take it inside with you wherever you're staying...like your luggage. No security issues. I love it for the price.
Minuses-
The attachment straps make it universal BUT you need to get creative and try several hookups. I'm still trying new ways to attach it.
The nylon straps may rub the paint over time. It hasn't happened to me yet and I have 3 long trips with it so far.
Because of the top zipper it's not going to be very waterproof but a garbage bag as a liner solves that. I also sprayed it with a tent sealer. Several coats.
The reviews I read before purchasing warned of over tightening the snap hooks. Apparently they may break. No problem there for me as I try to careful about that.
Sorry I don't have any pics of it. Hope this helps.