I have to make this comment.

If Elmer's glue is regular wood glue then it dries and becomes very brittle. I cannot see how that would be what one would be looking for, because the opening and closing of the bellows will eventually cause a crack.

I have used Evo stick mixed with black Hammorite. I made it into a paste put it on an envelope and allowed it to dry. I was then able to roll the envelope and the glue was quite flexable. I have used 3 light coats and have certainly sealed the holes for the time being. I have applied this to the outside of the bellows.

I just can't see how ELmer's (if it is normal wood glue) can do the job on a long term basis. I must point out I have never tried this before and I am prepared to be shot down in flames with my evo stick choice.