Need new seatbelt(s)

[ChrisZang]

My passenger's side seatbelt is stuck and I need to replace it:

It seems that seat belts are quite hard to find online, does anyone have a good source?
Quick poll:
a) If the passenger's side seatbelt is broken, shoudl I replace the driver's as well?
b) And if the answer is yes, in a different color (Red or yellow)?
Did anyone buy colored seatbelts and has a good source for it?

Thanks