Most bottles will fit, I tend to use the Gerber bottles because they are the cheapest and the parts are pretty universal. Plus you can buy replacement nipples for them.
You can use any bottle that fits and any storage bag. I personally like the Target brand storage bags, they are less expensive and seem a little thicker so less likely to leak.
WrongHas To Be Medela Or The Bottle Won't Fit. At Least That's What I've Been Told. Could Be Erring