The last firmware for the Kobo WiFi series (there were three versions) was 1.9.12
Nobody has a copy of the updater that can be copied to the Kobo. The Kobo desktop software no longer supports the WiFi models for copying books to it or firmware updates.
For archival purposes and continuing use of these, here's what to do with an N647, N647B, or N298 that has version 1.9.12 All three need imaged since the firmwares are not interchangeable.
The same software that's used for imaging and upgrading the internal micro SD cards in the Touch, Glo, and other Kobos with a removable card also works on the WiFi.
Remove the card and image it to save your settings, book progress etc.
Put it back in your Kobo WiFi and reset/wipe it.
Remove the card again and image it. Send the image file to
https://pgaskin.net/KoboStuff/kobofirmware.html The site seems to have all the Kobo firmwares for models released after the three WiFi ones.
Now you can either write the first image back to the original micro SD or write it to a larger card (it can take at least a 16 gig, probably tops out at 32 gig) and using the same utilities that work with newer models, expand the partition to use the expanded storage - and have all your settings etc as they were.
The one SD image available for the N647 model is version 1.9 and is registered to someone so the first thing that has to be done after writing it to the card and reassembling the Kobo is give it a reset.
When I got my N647 from a thrift store it was still supported and I was able to use the Kobo software for Windows to update its firmware. Earlier this year something got corrupted on it and the only fix was to wipe the micro SD and write a good image to it. The image was provided by one of the Mobileread members.
The Kobo WiFi is still a perfectly fine reader, small, lightweight, and when not having a corrupted SD card it still works with Calibre to put books on it.