You will need to call up Burton for some J-Bars (not sure if Burton shops have them). They used to ship J-Bars with their boots, but so few people used them they stopped. It would be nice if shops had them as well. Some might.
Footbeds are insoles. Most boots come with terrible footbeds. If you have a high arch or other such condition, it could cause pain because your feet are not supported. You can get aftermarket footbed you can stick in the oven and mold to your feet or you buy some that are custom fitted in the shop, which worked for me. There are many threads on footbeds.