Couch,
I got a set some time ago and I'm very happy with them. They keep everything really tidy and make it very easy when you're looking for stuff.
I've scanned my computer to see if I can find where I got them from and the cost but sorry, I can't find.
I think I got them from the states, they're red and have ST1300 embroidered on the pocket. I think they're larger that standard.
I've just looked on ebay and found these; Honda ST1300 ST 1300 Saddlebag Side Pannier Liners Red
Not sure if they're the same. They look VERY similar but mine look thicker. I actually use the left in the right and vice-verse. I do that because when I open the pannier the liner usually drops down with the lid. I then have access to the zipped pockets. Give it a try if you get some.