Archive quality storage

[ntw]

I am in the process of re-housing my collection, from the A4 ring binders/box files, to some customer made presentation files. As part of this I want to upgrade from the existing (sometimes cheap & nasty) punched pockets I have, to something more suitable for longer term storage.

I've found plenty of polypropylene punched pockets, which are pretty decent, but I'd prefer to go for polyethylene, or even polyester, given these are consider better for longer term preservation. However, I'm struggling to find punched pockets here (I can find plenty of sleeves, but they don't have the holes for filing); the only ones I've found so far are coming in 55p each, and given I need 3,000...

Anyone know of a manufacturer/supplier of these?

Similarly, for my oldest programmes, I'm going to go belt and braces, and will be using polyester (Mylar, Melinex, etc) sleeves for these, to go insider the punched pockets. I've seen what Preservation Equipment, Conservation by Design & Secol offer, but are there any other options here?