Internets
In the Department Store in Lilycove City. Basically in other Pokemon Marts, too when you have enough badges.
You can purchase Gallagher Girls badges from online marketplaces such as Etsy or eBay. You may also find unofficial replicas available for sale.
A good place from which to purchase toy plastic badges for children would be a store such as Party City or Toys R' Us. Several websites such as Party Cheap, Amazon, and eBay may have them as well.
On eBay
The ChiefSupply store provides people with military, firefighter and other special type of clothing. The public are limited to buying non harmful content only, such as badges, t-shirts.
There are 19 lots of 20p in 3.80 So you can buy 9 lots of 3 badges, which makes 19*3 = 57 badges.
You buy them at the poke-mart once you have enough badges
Yes, they sell iron-on patches.
There are many places to purchase pin badges. They can be bought online in store. Some of these places are giftshop, cancerresearchuk, bigcheesebadges, etsy and amazon.
if you want to buy things to do with gaming i think the best place is GAME the shop
eBay.com
you can get rep with the trolls and buy one or you can get badges from battlegrounds and get a warmount