Can Someone Help Me Find The Gadget I Describe?

Many years ago, I went into a camera shop. I told the man I need a way to photograph coins up close. He immediately asked what kind of camera I had. I told him I had a poloroid and a 10 mm camera.
Well he wasn't impressed ... LOL
But still he was very helpful and came up with a really neat lense.
Normally this attachemnt would have slid over the lense of a 35 mm camera and it had a square base of about 2x2 if I remember correctly, and maybe even larger.
The was a very distinct convex lense that was quite large and almost as big as the base.
He explained to me that when I took a picture of a coin without a correct lense that my plain camera will make the edges fuzzy as the close up shots were concentrating on the center of the coin and I lose detail as the image spread out away from the center.
This was supposed to flatten out the surface, and it did.

The long and short of this all is that gizmo was cheap and amazing. I had to hold it in one hand and take a picture with the other but it took great pictures and I think it made them 3x too.

I wish I knew what this attachment was called, I would like to locate another as I lost it and want to try taking pictures with one again with a digital. My digital pictures are not as good as I'd like them to be.

I think it was a Cannon product. It came in a vinyl pouch.
Thanks!