Bert Coules pretended :
My new integrated fridge-freezer came with a length of flexible soft white
plastic trim: right-angled, with one leg wider the other and an adhesive
strip down the wider part. It was to cover any gap between the edge of the
fridge-freezer and the side of the housing cabinet.

Does anyone know if this trim (or something similar) can be bought
separately? Various Google searches have turned up rigid hard-plastic
equivalents but not an exact match. I'd like to use it to cover an unsightly
gap between the side of a cupboard and an uneven wall.

Many thanks.

Just a suggestion, which might not be what you are looking for...

You can get white self adhesive bath sealer on a roll. As it unrolls,
it can be folded to a right angle, with the adhesive on both faces. The
adhesive is quite thick and goohie, will stick to anything once
pressure rolled on to spread the adhesive.