I can't find any bbq-pork pau's from the grocery store. I'd be happy with just the bbq-pork (char siew) without the pau.
I have had some other pork ones from the grocery storebut their fillines were a little dubious (maybe even gau?) But anyway, the other non-meaty, sweet ones are still okay - lotus, kaya for example. But try the ones in Suan Long.
I'm guessing that they only steam them when you order .. that's why you wait. There's not a rush for these so it's probably not worth their while for them to pre-steam. Pick a table near the fish, that would help.
BTW - the grocery stop near Bezirksgebaude tram stop actually do stock frozen dim sums from a restaurant in Geneva. Good tasting ones too and different to normal ones you get everywhere else. I'll see if I can dig up the address.