I know we already have a VIC20 core for the TC64, but someone on the Facebook group specifically requested that I look at porting the VIC20 core from MiST, so I've done just that.
And since a few people have asked in the past how I go about porting cores, I've put a series of videos on my Patreon page (not paywalled) where I talk about the process.
The core can be found here: http://retroramblings.net/?page_id=1765
Have fun!
(Please note: unlike the official VIC20 core, this one makes no attempt to do any kind of video framerate conversion, so you will need a 50Hz capable monitor. It does have a scandoubler, like the other cores I've ported - and this can be toggled by holding down the menu button / key for a second or two.