It's not that hard to get a local designer do you a full set of designs, with some basic brand guidelines for €3-5k. I've not done it myself but several client

It's not that hard to get a local designer do you a full set of designs, with some basic brand guidelines for €3-5k. I've not done it myself but several clients have. The brand guidelines I got from them, which I then used to style the app of the client, often included a website mockup, with the option of the client paying more for a full design. Not always the greatest UX though, that's a bit more specialized I think. As for finding them, ask your local startup groups. There's usually a bunch of them attending those sort of meetups, or people who would recommend someone.