There are many shops that stock the parts your after. Alot of people on here swear by "Pedders". They stock a variety of strut inserts and shockers. They also have lowered springs for your car.
Monroe also stock the parts, but are not very popular among most members.
There are heaps of other budget brands like "Gabrielle" (Supercheap Auto Special).
I have a set of "Kings" and "Lovells" Lowered springs sitting next to me for my KE30. Just waiting to the christmas break to do my girlock brake upgrade at the same time and see which spring will sit at the right height for me. I also have a set of "Boge" Strut inserts here that i plan to try out.
Then their are "Koni's". $$$$
If its for a road car, and you want value for money - Most people would suggest a set of Pedders lowered springs (or Custom Springs), matched up with some Pedders Shocks. I think i have Pedders Comfort Gas in mine at the moment.
My KE30 has an extra leaf in the rear and Pedders Gas Shockers. Its very stiff, but I like it that way.