There are multiple places to get medical marijuana in Maine. You should Google The Wellness Connection of Maine and try out some of their locations. One is at 685 Congress Street and their phone number is 207-689-9555, another one is located at 31 Main Avenue. There are quite a few places to find it.
You have to jump some hoops, but as long as you have a medical marijuana card from your home state you can buy the same way in Maine at a dispensary there. Make sure you have paperwork such as birth certificate, home state id, physician paperwork related to your medical marijuana card.
If you have a Medical Marijuana Card you can visit any of the state-licensed dispensaries in Maine, which you can get from specific doctors in the state. If you are not a resident of Maine, you must have appropriate authorization from another state. Patients must also register in Maine to be permitted to purchase marijuana there, which requires Maine-issued identification.