The Revanite Battler decoration can be dropped from Mid Rim Explorer's Packs, which were released on the Cartel Market and bought with Cartel Coins. Cartel Packs, including the Mid Rim Explorer's Pack, include a random selection of items from the Mid Rim Explorer's collection of items. You aren't guaranteed to get a Revanite Battler decoration from a Mid Rim Explorer's Pack, but it is one of the few ways to get a Revanite Battler deco apart from buying it on the GTN from another player.
If you're looking to get a Revanite Battler, the easiest way to get it is to head to the Galactic Trade Network (GTN) in SWTOR and buy it with credits from another player. If it's very rare and not available on the Cartel Market, you could try buying from the GTN and hope you get it.