If you need any help or just want a friend feel free to ask me.
As for your already asked question. Look here in fan art shops (Link) and you can find somebody to make one for you. Just make sure to read the first post to see if banners are one of the things they offer, that the shop is open and what they need from you for them to make it.
The two of you need to change friend codes on the pal pad.. You can orbit the pal pad by going into the WI-FI room in the Pokemon center. After you get it you change codes with the person and enter theirs in your pal pad.