Of course it exists, Corbyn can create it any time he wants.
I have to say, the idea people like you seem to have that Labour MPs would support some unelected "grandee" en masse - even if Corbyn said they should, itself highly unlikely - is far more improbable than that the leader of the opposition should be made PM for a few weeks to do literally one thing.
Total magical thinking.
Ah yes sorry, we all forgot that the parliamentary Labour party loves Jeremy Corbyn so much they will not accept anyone except him as Prime Minister...
Catch yourself on! You're the one magical thinking!
If this was truly about stopping no-deal (which it clearly isn't), obviously it wouldn't matter one bit if the Prime Minister is Corbyn or anyone else who support the idea of asking for an extension with the EU.