Water containers (Kennington OX1)

Does anyone have (or know a good source of) containers like this?

I'm making an effort to water the nice new street trees the council planted a few months ago, but I only have one container and obviously it would be more efficient and environmentally friendly if I could do several in one trip. Just carrying open buckets of water around isn't great, especially with all the speed bumps!

If I could get hold of some more containers like this, that previously contained something that wasn't particularly harmful, that would be great.

Does anyone have any suggestions, maybe catering establishments, healthcare, science labs...??

Happy to collect at a time to suit. Many thanks!