Where to find cel bags

I've decided that I should invest in some good quality cel bags. I know this has been discussed in another thread but what sort are best to buy in terms of protecting artwork?
I'm under the impression that the generic polypropolene ones (like comic bags) aren't acid free and would need to be changed every 5-8 years. I collect comics and use Mylars for my special ones because these are acid-free and look really nice, they are also very expensive and I couldn't afford to house my cels in these.

I don't like the type of bags that have the sealing strip either.

What I'm ideally after is the the plain 'standard' 300mm x 240mm (12" x 9.5") for keeping the cels in without the dougas. Rinkya offer good bags but they're not intentially made for cels.

Most importantly is shipping cost. It's all very well finding a reputable online retailer but if I have to spend $300 on delivery of 2000 bags to the UK, is it worth it?
Is there an equivalent type of bag I should look out for- either by brand name or material? One which I could buy over the counter in some store?

[sorry for all these ignorant Qs, I don't usually post such requests but spend a few hours reserching it myself, any reccomemdations from you folks that are in the know would help] ;)

Thankyou kindly!
Krafty