Mmmmm Actually I just go to several website from google, nengun, greenline. I actually have Apexi 440cc Injectors, greenline sell HKS injector for our cars ranging from the one that I mentioned b4 , same as sard and nismo injectors oh well that's the most popular choices.
Some people in Japan and UK use HKS and Sard because they supply bigger size injectors than Nismo.
We are only talking about bolt on job without changing the fuel rail.
I can't remember which website I went to but if you search about GTT injectors you should be able to find something useful.
Hope that helps. I'm pretty sure it's 99% accurate but who knows I might be wrong