This old video led me to ToFu, but you have to request access to run it, and they're selling it.

So I turned to these benchmarks, and HRN, code here. This one is nice because it's available on ModelScope. A Chinese translator and login away from simply building it. Very cool...

update Nov 2023 The model on ModelScope I used before to mild success no longer functions! This means I'll have to find something else. It appears that this model on the same website does full-facial reconstruction, and will even add eyeballs. So I'm going to give it a try using the code they present. I'm worried that (as with many algos) it will not work unless I have the training data.

Others could probably be run on my Mac, and on other hardware.

• The designer came in clutch though, not only producing something which resembles my dad, but creating a cartoony effect which will print really nicely.
  It seems the insert-picture option is disabled here unfortunately... Hmm...
• the api Face++ has a seemingly good API method. It gave reasonable results for one head (my mom's dad), and abysmal results for the other (my mom's mom).
• metaperson's avatar sdk gave abysmal results, not doing much to sculpt the face according to the image
• reallusion's Headshot Plug-in for Character Creator seems it may have good results, given it's paid ($149 for Character Creator 4).

some places already make busts

• FaceGen (link, from Toronto) seems to be the most developed, and specifically says "Create realistic 3D printable heads, busts, & statues". They have a demo
• my3dselfie (link) offers this bust-from-picture service for just $50. They're in color, and looks fantastic! They'll add glasses, wow.
• selfix (link) looks to be another great service. They're only offering bronze right now, at $2300 and $5000 (or perhaps they just don't have the prices there for the others)