Toyota Aeras - Year 2006 Suspension part Info

Hi 

I need replacement Spring Coil height adjuster [see attached pictures]  with the Ring mount which has to be replaced due to slow corrosion 

The installed suspension model is RS-R Ti2000 . As shown in the pic , the part within the rectangle is required with the ring mount [for both rear wheels]  I could not identify online what the part is called. If somebody can assist with the part name and any links where to purchase the part, it would be much appreciated 

Thanks,