I'm not sure if it's still alive, but if you're in Toronto, Ripley's Aquarium has one. Though, it's kept in the 'Canadian Waters' gallery for...reasons.
"Ripley’s Aquarium of Canada is home to a giant Pacific octopus (Enteroctopus dofleini). This species of octopus is the largest of 300+ known octopus species. There is a huge variation in size that depends on the individual, but the average for this species is considered around 15-18kg (33-40lb), with an arm span around 4m(12-14ft) when stretched out. Of course, we can’t talk about size without mentioning the world record – OVER 130kg (300lb) and 9m (30ft) wide! There has also been the occasional “fisherman’s tale” of even larger individuals, but the proof isn’t quite there yet.
The giant Pacific octopus can live to be about four years old, with both males and females dying soon after breeding. Females live long enough to tend to their eggs, but they do not eat during this months-long brooding period, and usually die soon afterwards."
"Ripley’s Aquarium of Canada is home to a giant Pacific octopus (Enteroctopus dofleini). This species of octopus is the largest of 300+ known octopus species. There is a huge variation in size that depends on the individual, but the average for this species is considered around 15-18kg (33-40lb), with an arm span around 4m(12-14ft) when stretched out. Of course, we can’t talk about size without mentioning the world record – OVER 130kg (300lb) and 9m (30ft) wide! There has also been the occasional “fisherman’s tale” of even larger individuals, but the proof isn’t quite there yet.
The giant Pacific octopus can live to be about four years old, with both males and females dying soon after breeding. Females live long enough to tend to their eggs, but they do not eat during this months-long brooding period, and usually die soon afterwards."
https://www.ripleyaquariums.com/canada/tag/qa/