Here are some photos for making your own flash diffuser for sb-400.
1. First photo shows the test shot of with the diffuser attach to the flash. Where else to test it best than the bathroom: light off, door close.
2. Next photo shows the empty glass-cleaner bottle (from Carrefour).
3. Aluminum container from chinese restaurant
4. Bottle cut just on top of label of the product. Aluminum cut to strip the width of what would be the back of the diffuser.
5. Bottle cut in to shape to fit the sb-400. Aluminum strip taped to the back of the diffuser.
6. Velcro tape attached to the edges of the bottle and to the flash. Remember to put the "hairy" side of the velcro to the flash so it will not stick to the case when you put it in.
7. Photos of the diffuser attached to the flash.