Westcott Pocket Box Mini Speedlight Softbox (6" x 7") - This compact modifier can easily fit inside a gear bag or backpack.
Godox 8" X 12" (20cm x 30cm) Mini Softbox f/ Speedlights - Ace Photo
Silver Reflector Flash Diffuser Softbox Professional Mini Photo Diffuser Soft Light Box for Canon Nikon Sony Camera|softbox canon|box diffusersoftbox for external flash - AliExpress
LumiQuest Mini Kit
Amazon.com : LumiQuest SoftBox III, Mini SoftBox Diffuser, Flash SoftBox Diffuser & Light Diffuser Photography, Small SoftBox, Portable SoftBox, Universal Design for External Camera Flashes, Black : Camera Flash Light Diffusers : Electronics