Don’t know who sells them but easy to make apparently. This from a web site I found:
I love amaretti biscuits, they are one of my favourite indulgences. I buy a tin of these every Christmas as a treat and have often wondered how they are made. I came across a recipe a little while ago and was surprised to find out how simple they are to make and they’re naturally gluten free.
180g Ground almonds
120g Caster sugar
1/2tsp Almond extract
1 pinch of salt
2 Egg whites
1 tbsp Honey
A handful Flaked almonds
Icing sugar
From here Gluten Free Recipe for Amaretti Biscuits