Quantity   Component name
1 × Wacom I2C digitizer (w9013) You can get it from Lenovo YOGA Book keyboard replacement part.
2 × 2kOhm resistor (mine use x2 1K 0603 as I don't have 2k) use this for I2C bus pull up.
1 × WT51822-S4AT module or any other nRF51822 module, I keep it small.
1 × Li-ion battery 3.7v 220mAh can be larger, no limit here.
1 × Li-ion charger board (both charge and use at the same time) any will be fine, depend on your battery capacity and type.
1 × toggle switch depend on your form factor, mine is built-into the charger board.