Amazon has a lot of bag options, too. I purchased 2" x 4" bags for my daylily seeds, but I am thinking that once I've finally gone through all 1,000 bags, I'll go to smaller bags because the larger bags are a bit big for most seed types. Maybe I'll use something more like this:
https://www.amazon.com/dp/B00AFRWKO2/
I think the idea about re-using the ziploc bags you get is a great idea! I'm all about recycling and trying to put less plastic into our environment, so I highly recommend it. Since your future harvests are likely to be from the things you're getting seeds for now, you may not even have to worry about erasing permanent marker labels off of the bags.