Help finding book about a couple that orders a child by mail [s]

[Fredd]

I"m looking for a book i read as a preteen. It was about a couple who gets a child by mail. The child comes as a powder (i think). They add water to create a person. Their son then befriends the child and teaches it how to act - even to the point of not being perfect and exhibiting some flaws to appear more human.

[Emily]

Possibly, this might be Conrad: The Factory-Made Boy.

[Fredd]

That's it! Thank you!