I LOVE those micro steam bags. I usually hand wash the parts at work and then every couple of days or so do a steam clean. Just be sure to follow the directions regarding steaming the tubing, I ruined a set of tubes once (accidentally used only 2 oz of water instead of 4 oz to steam them).
I called around to quite a few stores before I found replacement tubing. Toys R Us and a few other places had the bottles & replacement membranes, but it was the boutique/specialty stores and a medical supply shop that had all the rest of the parts (like different sized breast shields and tubing).