Some Topeak bags (front and rear) come with felt-covered foam pieces that have Velcro on the ends; I've never used them because they seem to soak up the volume I need for other stuff.

I suppose the key thing for me is that quite often, the contents of my bar bags change between rides. Certainly when I was using the Topeak Tour Guide bags with plenty of external pockets, I was making use to them to keep stuff in permanent places. It's just a shame that the plastic backing for the bar attachment on those bags was too light to retain its shape especially in hot weather.

Now I use the Ortleib more often, TT and Vintage Cyclist have given me some ideas to work with. Thanks.