I have the exact same issue, with the broken handle in almost the exact same pattern, also on the middle row left seat. I spent an entire day searching parts yesterday (didn't help the reference figure uses the same reference number on 2 different styled seats, both offered on the same model vehicles) to try and get some answers. From the spare parts catalogs and the attached photo, looks like we need to purchase the whole bottom section as a whole.
The attachment is what appears on yahoo.jp search when I look up part number 71826-58010-C0 but for whatever reason I receive a 403 Forbidden error when trying to go to the domain it comes from, so I can't get a hi-res version to actually read what that Toyota part sticker says.
"-C0" is the suffix for the colour "black."
"-A0" is the suffix for the colour "shell."
So I'm 90% sure the part number we need is 71826-58010-A0.
There's a 10% chance it's a completely different part 71834-58040-A0 because the manual and motorised diagrams both use the same reference ID. However, 71834-58040 is 1/3rd of the price and the motorised version doesn't require any (expensive) levers. Also, I can't find any images of 71834-58040.
