Does anyone have the part number for this bush which I believe is the rear control arm. Would it be better off to just replace it with an aftermarket option like Superpro?

 

Outer toe-link bushing.
Search this section for Ray Crowe’s number. Probably the best price and you won’t need the part number.
edit: Just noticed you’re in Malaysia. Not certain on RC’s international shipping.
Sorry, all I have at hand is the part number for the entire toe link (FD02-28-450) but I’m pretty sure you can still just buy the bushings. Personally not a big fan of aftermarket bushings in a relatively stock and street driven car. If this is the case then stay with stock…IMO.

 

As mentioned above, that is the toe link.
If you get an aftermarket poly bushing, be aware that it can be a bitch to press the bushing in if it is one piece.
I run aftermarket rod ends for the toe link mostly because cost and install is easier but the stock bushing is pretty good too and lasts longer.

 

Just checked the stock arm (FD02-28-450) is quite pricey. I guess will have to get the bush only instead.

 

Yes, nothing in the arm itself wears out. Just the bushings. Can’t remember which bushing (inner or outer) but one has an aluminum or aluminum-like sleeve that requires a little more care to make sure it’s started straight so it doesn’t deform. It’ll be apparent which when you get them.
If you’re doing it yourself just clean the casing of the arm really well after pressing out the old bushings and use a bit of lube with the new ones. It’s pretty straightforward otherwise.