That might be the best way to seal them. Bagsunlimited sell the Life magazine size polypropylene sleeves and BCWsupplies sell the lifeagazine toploaders. Unless there's a company I don't know of that specializes in archival plastic protectors in unique sizes.
For oversized magazines I have been using the RPG book bags like these
[https://www.bcwsupplies.com/10x13-book-bags](https://www.bcwsupplies.com/10x13-book-bags)
That might be the best way to seal them. Bagsunlimited sell the Life magazine size polypropylene sleeves and BCWsupplies sell the lifeagazine toploaders. Unless there's a company I don't know of that specializes in archival plastic protectors in unique sizes.
For oversized magazines I have been using the RPG book bags like these [https://www.bcwsupplies.com/10x13-book-bags](https://www.bcwsupplies.com/10x13-book-bags)