I found that a certain unit by T'eyes which seems to be the most recommended on clublexus. Think I'm gonna go with that after I get confirmation that all of the required wiring harnesses would be present. Otherwise, the newest iPad I have is an iPad 2, so the infotainment option won't really work (unless there's a tweak which turns it into a Carplay receiver). Also, I don't think the double dinn would work, as I saw teardowns, where it appears that the control unit is separately located (under the glovebox) from the screen.
Edit: And the screen appears to be too thin to accomodate a full double dinn head unit (which is why these aftermarket ones seem to push the display a fair bit forward)
It does look like there aren't many (reputable) options, but I found this, which appears to be a less expensive reselling of a T'eyes CC3 head unit, which appears to be recommended on Club Lexus. I have contacted the reseller to confirm this, and ask if all required wiring harnesses would be provided, but I think this is the head unit I will end up installing.