I bought the 3S battery and it took me 24 hours to break it. You absolutely need the BL540250 strap to hold it as it's much larger than the original battery. Otherwise you'll have to use clamps to hold it in place.
For the charger, it's better to buy a conventional charger (skyRC, Robitronic...) which will be able to charge the 2s, 3s and even more anyway. You shouldn't buy just any 3s USB charger either, as there's an amperage limit for charging. The ref of the official USB charger is BL540249