Pushchair Connectors Compatible for Babyzen YOYO2 /YOYO+ Strollers, Turns Two Single Strollers into a Double Stroller : Amazon.co.uk: Baby Products
BABYZEN YOYO Connect, Black - Turn Your YOYO2 Pushchair into a Double Pushchair - Still Compact & Easy to Manoeuvre : Amazon.co.uk: Stationery & Office Supplies
Babyzen YoYo² Twin Setup with Connectors (Side by Side) - TinyExplorers