4000 series logic with TTL inputs?
In the end I opted for ULN2003 chips with 10K pullup resistors. Only tiny currents (nA or even less) are needed for the anodes and grids, so 10K is perfectly fine.  As it turned out I really needed around 30V rather than the 12V I was planning to get good brightness from the VDF when multiplexing 1:9, so the ULN2003 was perfect for the job.

Kudos to @oldfart for reminding me of the existence of them.