I bought mine from ultrafine online/photo warehouse.
Myself and a buddy teamed up to split the shipping and ordered a few things.
I ordered enough negative filer pages for all of the 35mm and 120 film I had in the freezer.
I figured that paying for the filers at one time would make me realize the horde I had built up and slow down on buying more film.
Well almost $200 in filer sleeve pages later it has been quite a while since I thought about buying and freezing more film until I use quite a bit of it up.