I desesperately need a reference. One of the modules I took in my masters was partly done (lab part) by a "non academic" professional. Is it acceptable to ask him for a reference even though he barely remember me ?
You can always email people there is no harm done, just ask in the email if they remember you (they might). They might not feel comfortable writing you one but they can just say that, it's worth a try!
Obviously respect their response whatever it is.
Also bear in mind that the reference is unlikely to be a strong one given the circumstances so you should try and contact academics you have had closer contact with first.