1)where can I buy laura ash paint in shop 2) how do people buy smaller paint amounts eg eggshell for bed

[RoseandVioletCreams]

I only need a small amount. I don't need 750ml is there a hack?

My local shop did a one off 250ml can.

Sample pots. Some can be enough for small jobs. Depends on the manufacturer what sizes they do, look online. Generally specially mixed colours only come in very small tester kits or at least 2 1/2 L. Some paints I use only come in 5L.
Make sure you have all your undercoating done in the right colour so you need as little as possible of the topcoat.