Yes I got 7 of them in a box, and one modded C64DTV (and one unopened), so no need for yet another one.
To my knowloedge there's the asic in the C64 DTV by Jeri Ellsworth (does not support cartridge port), and there is an FPGA version used in the Chameleon project (not open source), and some emulated one with an STM32.
And then there is that C1 also by Jeri. But it's far from a single chip.
A C64 is a quite complex bastard not easily done properly in a single chip.
It is possible to emulate it on one of the many available single board computers.
But this campaing smells bad.