Help me find a booster seat

[poppet31]

Hi, looking for some advice please. I'm looking for some sort of booster seat for my table for a two year old but our chairs are really awkwardly shaped (see attached pic) and I can't seem to find one that would strap around them. Any ideas? Thanks.

would this work? it has a curved back so might fit

What about raising the height of the chair so you wouldn't need a booster seat? these are aimed at older people but no reason why they wouldn't work for a child.

The two year old I look after has never used a booster seat. She stopped using her high chair around 19-20 months and has happily knelt on the wooden bench for all her meals since. She has a stokke tripp trapp chair that she can use but she prefers the bench.