Go on Amazon and check out Playmobil. They have some really great sets with lots of price options. Themes range from princesses and fairies all the way to police and farming. I highly recommend a set that comes in a little briefcase style box so they can keep the parts together when not in use.
FYI the briefcases are usually big enough to hold two small sets. So for example, if you like the vet idea below, you could get a supplemental pet set in a cardboard box and it would likely all be able to be stored in the case.
Sometimes pricing on Amazon is high, so be sure to shop on Playmobil’s direct website to price compare.