Do you know if you still have a number for whomever custom made them for you?I replaced mine several times as well. I was one of the earliest members to run the kit so I actually ended up have one custom made after going through 3 of them. Since the kit gained popularity a company called BOE fabrication actually came out with a reinforced bracket set specifically designed for the celica. If I were you I go for that option.
Damn, been searching everywhere as im pretty sure Greddy had them discontinued^^^ BOE does not make a kit any more. So the best scenario is to find a used set from somebody who upgraded to BOE.
Thanks for commenting