Hook on High Chair,Portable Foldable High Chair for Babies 6-36 Months, Includes Storage Bag (Black)

You can also get high chairs which clamp directly onto the bench, though you'll have to check safety based on age and weight. A one-year-old might not fit one for much longer. This for example: https://www.amazon.com.au/Toddlers-Portable-Foldable-Travel-Storage/dp/B0D59YY3VK