Shouldn't be too hard without a tut.
Go to action handler, firstclicknpc, make it execute a dialogue.
In that dialogue add options such as: Buy cape, never mind.
in clicking buttons, check for the button being pressed and then check for the requirements to receive the cape.
If requirements are met, give cape, if not, send error message.
You can do this for each master with certain id for each cape.
Hopefully this was helpful, if you need more help, just post back