A large cooler/eski might work best. To be honest, I am a big fan of the vertical trash can as well. I know many people and athletes who use small kiddie pools, try pool stores or Big W in Australia, or Walmart/Fred Meyer/Winco in America.
However, have you considered the science behind ice baths?
Do they actually work? Well, from a sports medicine standpoint there isn't much evidence to say they promote an anti-inflammatory response or reduce DOMS (delayed onset muscle soreness), and more research is definitely required in the effects of Ice Bathing after HIIT sessions. There are better recovery methods out there, that have more scientific backing. I like to diversify my recovery methods across the week.
So, then why do they make us feel good then, doesn't every elite runner ice bath?
The placebo effect may arise from the fact that the CWI (cold water immersion) causes vasoconstriction (narrowing of the arterial vessels in the peripheries) and the feeling of the warm blood rushing in from the core when one gets out of the bath can give an invigorating feeling and make you feel good. This gives the feeling of improved perceived recovery. It also may decrease the effects of heat and humidity, if the athlete is playing or training in those types of environmental conditions, by lowering the core temperature a degree or so.
I go into a lot more depth here, if you're interested in giving it a read, please click my link:
https://larahamilton.com/ice-bath-after-running/