World of Disney is the best place to find lanyards, bags and pin at DTD. They will take the AP or Disney Club discount too, so you may save some money.
You can also find pins and lanyards at the Pin Cart across from the Pooh Store.
I think the lanyard with the 2 Mickey and 2 Minnie pins sells for $20 or $24. You get a set of Mickey and Minnie to keep and a set to trade.
You can also pick up lanyards at any of the parks. I am not sure if they have bags at the parks, someone else might know the answer to this. Peggie