Recover corrupt mp4 video showing as .rsv

[DigitalMetal]

Hi,
I was recording some video on My Sony Alpha ZV-E1 camera and the battery ran out before the recording was finished.
When I powered back on the video file was missing from the playback library in the camera. I moved the SD card to my computer and there is a file several gigabytes in size with a file type extension of .RSV rather than .MP4 this must be the video file that has not wrapped into the MP4 container, no doubt because the finish recording command was not initiated before the battery ran out.
Is there any way to restore the file to an MP4 ?
I've seen one company online offering a service but its very expensive and many file recovery software companies advertising file recovery from failed memory or hard drives but no other options.
Surely Sony have a way to recover these files if this 3rd party are offering it (albeit at great expense) ?
I've tried the recover database option in the camera and that didn't help.
Thanks to anyone that has done this before and can offer a solid answer rather than speculation - the internet has too much of that  

[danardeng]

Try to contact sony support directly