Is it possible to make the gem bags, potion bags and scroll cases that occur in "Icewind Dale" appear also in Baldur's Gate? If so, how would you go about it?

I love those thingies, since it seems ridiculous to have the party overburdened with tiny gems and scrolls.

Not without cheating. Or including an unofficial expansion.

That's right, you could download a hacked bag of holding (which I have never used but I am told acts like a store, i.e. you can sell the items any time, anywhere). You can get that at http://www.execulink.com/~cmohan/aru.../bg_misc.html. And although I have not come across it yet myself I have heard rumors of a bag of holding (perhaps as just desrcibed? dunno) in Dark Side of the Coast, an add-on (technically an "add-in") or mod to ToSC. http://www.dsotsc.com/

The bag of holding mentioned above does act like a store, but it buys items from you and sells them back to you for the same price.