How can i convince my parents to letting me shop online?

(I am 12 and dont have a credit card)Well earlier today,i was bored so i went to my book shelf to check out books. Then i found 5 of my simpson's comics.then i thought about how cool it would be to collect simpson's comics. so i was thinking where did i buy my old comics and i remembered tht i bo ught them at my school book fair. But i cnt buy comics from there cuz its only 1ce a year. And i cnt go to a comic store cuz i dnt live near 1. so my only choice is online. I told my parents about it and they said its too risky and that they charge too much. Im buying from amazon and its not expensive. its like 10 dollars per book (i want to buy 5). ik amazon isnt risky and its safe but i dnt think theyll believe me. the total amount im thinking of spending is 47 bucks 4 these comics. i have the money but the thing is is tht i dnt have a credit card which u need to purchase items with. nd i REALLy want these comics. and i have good grades already (six A's and one C). I JUST NEED THEM TO PUT THEIR credit card number and confirm the purchase and i'll pay them. how can i convince them??