I recall you used to produce paint for concrete garden ornaments and offered them in500ml containers. Is this still the case?
It may be Ardenbrite Metallic Paint you are looking for, unfortunately this is currently unavailable.
Assuming you do not require a metallic finish, the concrete is bare, clean, dry, sound and prepared as detailed in the Technical data sheet we can recommend Coo-Var Acrylic Floor Paint.
This is available in 1ltr, 2.5 or 5ltr tins and can be mixed to many RAL and BS colours.