'Domestique' behind the seat bottle holder..........fitted one to my original 550- it was a tight fit for a 75cl bottle over the pivot- then discovered that you can't actually reach behind your arse that well in a head down/arse up setup. And one day, going down a long hill on road, I adopted the Eyetalian stylee descent posture, and planted my baws right on the thing...........never used it ever again- it now resides with my Chocolate Fireguard collection.
Cheers,
Dav
*PS- never used them, but I think they'd look cool- Kellogs Spokey Reflectors, shaped like the Cornflakes chicken- been knockin' around my toolbox for years- the better, more expensive, classic the bike, they look even cooler by dint of their extreme crapness in comparison.