Since official production has ceased, your best options for "new" units are:
: Sites like Draw My Pad may still carry stock of customized or refurbished new-condition controllers. DS 4 Die-Cast Models (Alternative to Paper) buy new ds4
Finding a "new" DS4 usually refers to the controller, which is increasingly rare as Sony has officially ended production. If you are looking for a papercraft version ("solid paper"), you can find DIY model kits and printable templates online. Papercraft & DIY Models Since official production has ceased, your best options
If you prefer a pre-built "solid" small-scale model rather than paper: Since official production has ceased