Air Bag, Cylinder Misfire & TPM

[dakenny]

Hi all, I just bought a 2nd hand Z4 2.5 E85 2003 model. Its also my first time owning BMW. I have got 3 indication signal. Airbag, Engine and TPM. I'm from Sandakan, Sabah. It's hard to get BMW parts here so may need all your help. Went to diagnose and found out that the Engine code: 2743 Misfire, cylinder 5. The mechanic says I need to change the ignition coil. Anyone could recommend where to get cheap BMW parts? Contact?Second is the Air Bag code: Air Bag Under Voltage. The technician says needs time to slowly check this problem. Anyone of you has encountered this problem before?Third is the TPM. I have checked my tyre pressure in a balance pressure, then turn key until 2nd(engine off), then press and hold the TPM. I hold for 20seconds and the TPM signal is still in red. Need your help.