The Arrangement: Spacer’s Lounge deco is part of the Spacer's Bundle, a set of decorations that you can buy directly from the Cartel Market with Cartel Coins. All decorations from the cartel market, including the Arrangement: Spacer’s Lounge deco, can usually be found on the Galactic Trade Network (GTN) and bought from other players with credits.
If you're looking to get an Arrangement: Spacer’s Lounge, 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. You can also buy the full Spacer's Bundle from the cartel market or GTN, which includes this deco and a few others that match.
The Arrangement: Spacer’s Lounge deco can also be bought straight from the Cartel Market for 110 Cartel Coins.