Does the loan letter have to be from a bank? or can it be from a uk resident who is willing to provide the funds

Hi, I have found myself stuck in the most complex of situations, my tier 4 visa expires in 4 days (sept 11). Now I have fully paid my course fees, and have cas number. My only dilemma is that the maintenance funds were only put in for 4 days, I am applying for an extension as I am in the uk ...