A number of types of dolls house flowerpots are available for miniature plants. The wooden plant pots from a craft store are a good size, but the rims are out of proportion to the pot.
Use sand paper to reduce the edge (The pot on your right in the photo is the one that was sanded to a better scale). You can use sandpaper to take off rough edges on soft terracotta pots as well, if you want to make rims the correct scale.
