Edit: SOLVED, see comments
I have a K4 Hatchback GT-Line Limited (Canada). For cost cutting reasons, Kia outfitted the driver's side with power controls and lumbar, while the passenger side is fully manual with zero lumbar support.
My partner is 4'11" and sinks into the passenger seat so much her legs are kicked up, but she fits fine in my driver's seat thanks to the lumbar support. It's quite uncomfortable for her.
Is there any reasonable way to retrofit the lumbar support on the passenger side short of importing an AUDM or UKDM seat? Finding a mesh lumbar support that's only 1 ft wide is pretty difficult, a foam support would prevent the cooled and heated seats from functioning as intended. An aftermarket lumbar bladder is also an option. I can't find any clear parts diagrams or pictures for this car's seats unfortunately, so until I open up one of the seat backs, I have no idea what I'm dealing with, where the heating elements are, etc.
You probably can add it by buying the parts, disassembling the seat, mounting it, then changing out the seat cover.
The cost would be seriously prohibitive. The seat cover alone is probably hundreds of dollars. As are the lumbar parts and controls.
It would be easier and more cost effective to get a driver's seat from a junkyard/ebay and swapping parts or as much of the seat as you can (often seat backs are interchangeable as a unit).
Or, spend $19.99 on Amazon for an aftermarket adjustable bolster. You really won't lose much seat heating/cooling since it's just the bolster.
I actually figured it out, the seat back is a lot easier to remove than I thought.
The bladder is just this black pad with a bottle behind it. It can be easily retrofitted or an aftermarket bladder with a hand pump can be fitted. Barely any disassembly needed.