I have a fisher brand wood stove with a 7.5” opening that I’m trying to install
I can only find a 7” to 6” reducer which is too small
Or a 8” to 6” reducer which is too large. I have tried bending and snipping the 8” reducer
But it just doesn’t want to work right. See photos.
Any advice is greatly appreciated .

I'd have a reducer fabricated that you can bolt or weld on the stove.

A 7" pipe with a flange welded over the hole with the pipe stub up. Or a ring welded into the hole to make it 7" or 6" A piece of 1/4" flat rolled into a ting to fit the hole should make it 7"

US Stove parts
Pittsburg (with no h) Tennessee.

Reducer is not the part name you need.

A fireplace store can help you.

Think it's called a "adapter"

Edit* maybe not, I'm seeing reducer & increaser when the pipe dimension differs from the stove collar.

Do you have a local commercial HVAC shop? They can build one out of 16 gauge black iron. You want a reducer. 8" I.D. to 7 3/8;" O.D. with 1½" collars on each end, so the small end (7 3/8") fits into the stove and the large end (8" I.D.) goes over the crimped end of the pipe. 10 inches in total length would be easy to fab. The collars could vary depending on how much can go into the opening on the stove. A welding shop could fab this also.