most skill trainers sell them but at lions arch there is this guy near the skill trainer that has this quest that u do that u use capture sig and wen ur done talk to him and heel give it to u again then talk to him and u can buy it from him once u have used the 1 he gave u- Fm Shadow (my main)

where do i get the next set of armor after the charr set?

For armour after the charr armour u go to la or droknars or anywere else past shiverpeak

http://wiki.guildwars.com/wiki/Main_Page

http://guildwars.wikia.com/wiki/Main_Page