Thin wheel spacers

I have 305/50/20 cooper zeons on 20x9 bmf novakanes with 5" backspace and the tires didnt rub when i have 275s but they touch a little now at full lock. Does anyone make a 1/4 inch wheel spacer that isnt cast aluminum or are those actually safe. All the ones ive seen look like really poor quality material and castings.

I carry cast aluminum ones and never have any issues with them. Probably about 300-400 customers buy them.