Hat jemand Empfehlungen für einen Ort, wo ich das in Helsinki machen kann?

I’d personally go with something like Vistaprint but there’s a Lohikari Oy store in Helsinki center that sells those roll-up banners, they don’t seem to list prices though.

Also you can try to google the words „Roll-up mainosbanneri“ or „Roll-up mainosständi“ to find a store that fits what you’re looking for.

https://markkinointitarvike.fi/roll-up-telineet/18-roll-up-85×200-standard.html

Worked with them for few marketing items, our experience was good