Drinking glass question

I recently broke my dad’s favorite glass. He uses it for bourbon, but I’m not sure if it’s a “bourbon glass.” I’m trying to find a replacement (he already knows I broke it and it was customized, so I’m not trying to hide it or anything). It’s pretty much a normal glass but instead the bottom half has like a curve, I attached this photo to better understand.

Can anyone find me a glass like this? Or tell me what this type of glass is called?