Where do you get a set of (metric) thin open end wrenches

about to remove the rear calipers on my VW and there's a thin wrench (there's a term for this other than just simply called a thin wrench) that is just like a regular open end wrench but thin enough to squeeze into a tight space to hold the caliper bolt in place. A socket won't work because the bolt to be held is not accessible at the ends.

(Note the picture shows a regular wrench but in my case, the last time I did it a regular wrench was too thick to fit in there.

Tried Home Depot, NAPA, Sears, Advance Auto parts, nothing even close ... what are these wrenches called and where do I get them before this weekend when I planned to change out my pads and flush the lines?

Any help is appreciated, thks

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Where do you get a set of (metric) thin open end wrenches