There's lots of good ones, but the previous owner gave me a 'Bags Connection' Trial QL bag, and there's no way I'll go back to my old ones or anything else.
It mounts on a little ring that installs on the gas tank ring and it locks on there, and you pull a little cord on the bag to release the connectin, they have a firm bottom and that bag sits perfect and flush on the FJR, does not touch your paint at all, and the quality of the bag is top notch, lots of expandability. They're pricey but if I had to spend my own money on it I would now that I have one.
https://www.twistedthrottle.com/trade/productview/2624/451/
edit: ^ What he said ^