google doc guide of how to purchase copyright
ISBN's can be bought individually and are sold without OR with the barcode. To save money on purchasing an ISBN, I suggest buying from a official website. Bowker is one of the most widely recognized sites for purchasing http://www.bowker.com/products/ISBN-US.html But I know there's a few others.
LuLu's sales works like this: If you opt to sell outside of just Lulu's marketplace (amazon, barnes and noble, ect) then you will automatically get a free ISBN for your book.
If you opt to sell privately or just to Lulu's marketplace, you get a custom product number which is placed on the back of your book as "A look alike ISBN" to the untrained person, but this number cannot be used to search up your book on amazon or anywhere. It's strictly just for Lulu and will appear on your cover, period.
If I recall correctly, your book going through amazon, the physical book will not have both barcodes on the back - just the one which is more important. IE if you go "outside lulu's market" it has the ISBN, if it you "just in Lulu's market" it has their barcode.
I can give some lulu vs createspace comparisons between paperstock and coloring of covers, and what not for novels. For comics, I know from asking artists at Artist Alley that they'd rather sell their soul to Kablaam or any other company before their work get touched by CreateSpace (lots just overall disliked CreateSpace's physical product.)