I understand why some people are hot to trot on those 120 spools...
Not so long ago I stumbled upon an article on modifying your 35mm film for use in...
You guessed it... Holga Cameras.
You use the paper backing from a roll of 120 to tape the end of a roll of 35mm film.
The film is turned with the emulsion side to the backing such that the exposure is made THROUGH the backside
of the 35mm film... requires extra 2 or 3 fstops exposure to get a usable image.
The film is hand wound onto the 120 spool and 35mm film is then cut to fit to the end of the paper backing.
Of course, this is either done in a change bag or a darkroom.
Take your fabricated roll of "Holga Special" and load it into any 120 MF camera.
I just might have a go at it someday in my Bronica.