Perhaps those sold by biotech companies have stricter requirements? As in, they have more even pores distribution/size or whatever? Is this for like, FYP or something? Or like, is it a research grant that you need to skimp on? Don't think it's wise to waste all your DNA extraction, all those enzymes and chemicals, not to mention time and effort... haha! Not you pay also right? ;p
If still need cellophane, I dunno... did you ask the staff at Art Friend? Or the Bras Basah Popular? Tried Sagacity? They're not at Bras Basah anymore though... moved to somewhere quite ulu... can't remember where.
When I was in poly, the school supplied all the gels we needed... didn't need to think about cost. Haha!