how to add extra beats in a crooked tune

I am creating tab for a crooked tune by the Québécois accordion player Réjean Lizotte.  The tune is basically in 4/4 time, but there are 2 extra beats in between what would be the fourth and fifth measures.  Should the fourth measure be written in 6/4 or should I add a measure of 2/4 after that fourth measure?  Is there a standard answer?  

I know this won't affect how the tune is played, but I wonder if there is a standard approach.

You shouldn't need to hear to the tune to answer this question, but if anyone is interested, here it is .  [Beware: it's an ear worm!]