idk

i bought toyota red coolant, pour all in and top up with water.

not ideal, but it works

there is a lot of black plastic thing on the door, which one you are talking about ?
if you mean came off while driving, I think its the sun / rain visor ?



if yes, then u can get after market ones, no need use ori.
Ori ones doesnt come cheap either 

It's prolly one of the items described as "Quarter panel" in the parts list.

The best way to check would be to find a Gaga, (and with the owner's permision) cabut the panel and note the part no.

 
Go SC, then ask them for it to double confirm.
In their PC, they will have exploded drawings with BOM including up to the pieces of nuts and washers.
From there they can click click and click until they reach the part you mentioned.
Then, either you ask them to book for you (mostly they dont have such part).
Or you can get the part no. then go Glenmarie Spare Part Centre and try got or not.
Plis call Glenmarie SP Centre before you go, otherwise if dont have, don whack me for wasting petrol 
Most SC get their stock from them anyway 

I am not sure whether spare stockist carry them or not.
I usually just go normal SC or straight Glenmarie SP centre for such not common changed parts.