The panty hose thing doesn't work for long- from my own experience I would advise giving it a miss. The seachem bags are the best because they stand up to the concentrated bleach solution you need to recharge the purigen in. The bags you buy seperately are a lot bigger than the pre made baggies, but you will need zip ties to close them.
I got some stretchy bags from eBay that are okay, but I haven't used them long enough to say how they stand up to the bleaching process.
Unless you only want tiny portions, it is more economical and convenient to use the bulk purigen and buy the large bags rather than use multiple baggies. Baggies are great for HOBs.