Bought a car in Neu-Isenburg and gonna need the umweltplakette. Where do I get it in the morning hours?

Hello everyone.

I've bought my first new car in Germany (Thanks for that!) and I'm gonna be picking it up from Neu-Isenburg and driving to berlin. The thing is I totally forgot to order the umweltplakette in advance.

Where in Neu-Isenburg I will be able to buy it in the morning (around 10 AM) that I'll be sure they'll have it for sure?

Apologies if it's a dumb question, but I seriously not sure how this thing works.