Custom OEM size/fit has been addressed to some degree for a quite a while now by both the "mainstream" car audio manufacturers [1] and, more extensively, by some lesser-known aftermarket brands [2].
YMMV based on just how old your car is and the type of OEM head unit, but there are kits (e.g. this one for a 2016+ Honda Civic [3]) that allow you to install "standard" head units with a fit/style similar to OEM.