Bought and sold on the GTN from other players
Bought with Cartel Certificates
The Arrangement: Speeder Station decoration costs 2 Cartel Certificates and can be bought from the Cartel Market Certificate vendor, who is found on the fleet in the Strongholds & Crew Skills section, near where you can purchase decorations for credits and where you can buy your stronghold.
Cartel Certificates are extremely rare, and only drop from some of the older Cartel Packs and as a rare drop from the Contraband Slot Machine.
If you're looking to get a Arrangement: Speeder Station deco and don't have any Cartel Market Certificates, this type of decorations can be bought and sold on the GTN - but they are usually quite expensive due to the scarcity of the Cartel Market Certificates.