Hi A.,
I just finished breastfeeding my second child with an Ameda Purely Yours breast pump. While it didn't come with a bag, I used the black bag that I received at the hospital from Similac that came with the insulated bag and ice packs. It worked perfectly for both of my children.
I read through the responses and the one thing I did not see mentioned was the difference in functionality. When I was shopping for a breast pump my lactation consultant showed me several different kinds including the one's mentioned in previous responses. She then demonstrated how each worked, the pros and cons of each, etc. What sold me was that the Ameda is the only one with a closed system- meaning that milk could not backflow into the pumping system. The other pumps had an open system which meant that when milk flows back into the system it can create mold and potentially get into the fresh milk being pumped. The open system is the reason women don't share pumps. With the closed system though the parts are more simplistic and everything can be cleaned. She said essentially that while it is not recommended to share pumps it would be possible with a closed system. They just don't recommend it because most people don't realize there is a difference. This is also the difference for the pumps you can rent versus purchase.
My suggestion would be to go to your lactation consultant and talk with them. Hopefully they are knowledgable about the pumps they are selling. I purchased mine through the hospital at Rush-Copley on 34 in Aurora about 3 years ago. I have been very happy with how it has performed. I was able to purchase replacement parts when needed through momsonline.com.
Blessings and Best Wishes,
L.