This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
Here are places to try ... Grace Ashley (352-748-7739, http://apple2software.htmlplanet.com/ ) sells Apple II educational software and 'blank' 5.25" diskettes Albert Franklin (email: email@example.com) sells 5.25" DS/DD diskettes. XDR2.com ( http://www.xdr2.com/ click on "Disks") sells 5.25" and 3.5" DD diskettes in bulk (e.g. 50 3.5" for $13). Meritline.com ( http://store.yahoo.com/meritline/floppydisk.html ) sells 3.5" DD diskettes in bulk (e.g. 100 for $14). Peripheral Manufacturing, Inc (800-468-6888; email: firstname.lastname@example.org ) sells 5.25" DD diskettes in 10 packs ($2.95) and 50 packs (with sleeves, $15.00).. Commodore 64 & 128 Products ( http://www.oldsoftware.com/Commodore.html search the page for disks for sale) sells 5.25" & 3.5" DD diskettes. Check the non-Apple sections on eBay. Sometimes you'll see boxes of a thousand disks going for the cost of shipping -- if they're listed outside of Vintage Apple they seem to go a lot cheaper. Thrift shops: you may find packs of used 5.25" DD diskettes at bargain prices. By: David Wilson