Is there any current source of those 3D CPK kits?

You have to distinguish space-filling and semi-space filling, see below:

For semi-space filling, many ball-and-stick models also have pegs instead of sticks to connect atoms without extra space between them, like this Molymod Biochemistry set:

It is more difficult (and more expensive) to find space-filling model kits, but they still exist, e.g. this HGS model kit:

History

Space-filling models are associated with the CPK initials because Corey and Pauling published a home-grown non-commercial space-filling model in 1953, and later Corey, Pauling and Koltun made them available commercially.

Is there any current source of those 3D CPK kits?

You have to distinguish space-filling and semi-space filling, see below:

For semi-space filling, many ball-and-stick models also have pegs instead of sticks to connect atoms without extra space between them, like this Molymod Biochemistry set:

It is more difficult (and more expensive) to find space-filling model kits, but they still exist, e.g. this HGS model kit:

History

Space-filling models are associated with the CPK initials because Corey and Pauling published a home-grown non-commercial space-filling model in 1953, and later Corey, Pauling and Koltun made them available commercially.

They were sold by a company called Ealing, and searching for "Ealing CPK" might lead you to a vintage model such as this one: