Hook: Floor Large (Purple Square)The Hot Spring decoration fits into a large purple square floor hook.
How to Get a Hot Spring Decoration
Cartel Pack Decorations
The Hot Spring decoration can be dropped from Spoils of War PacksUltimate Cartel Packs, which were released on the Cartel Market and bought with Cartel Coins. Cartel Packs, including the Spoils of War PackUltimate Cartel Pack, include a random selection of items from the Spoils of War Ultimate Cartel collection of items. You aren't guaranteed to get a Hot Spring decoration from a Spoils of War PackUltimate Cartel Pack, but it is one of the few ways to get a Hot Spring deco apart from buying it on the GTN from another player.
If you're looking to get a Hot Spring, 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.