ProPhoto is a great shop, definitely old school. I recently picked up some Ilford B&W 120 from them. Not sure they have Colour 120, but would not be surprised if they do. They still carry chemicals (dry and liquid) and paper. They repair equipment on site too. They have some nice used gear and some real used gems from time to time, several display cases full of used gear. Older owner who is full of knowledge and polite as well as humble. One of favourite shops.
Penn on E Street is well stocked with 120 film too, better than 18th Street. Some nice used gear too from time to time. Nice people here too.
If your plans change and you find yourself heading up to Baltimore, then you owe yourself a trip to Service Photo. Well stocked with 120 film, great group of people and some nice cases of used gear too.