So far as I can see, the answer is, either find a snazzy way to tape it to your bike without blocking the LEDs, or maybe get some tough rubber bands and put them around the seat post and try and strap the light on that way. Failing all other creative ways of lashing the lamp to your bike (which may not be too handy if you want to re-charge it regularly !), then I'm afraid you may have to place it on a shelf and gaze wistfully at it, or just throw the thing away.
The rubber strap on mine broke very quickly, so I am deeply not impressed with this feature of an otherwise nice little lamp.

flanges using

Elastic band, after taking your saddle off to get it round. Or use it as a bedside lamp.

Or throw it away.

Cable ties?

The band seems very good quality, I can't see it wearing out. If it's handled with care it should last years.

Throw it away

Fair question - it's possibly the only design flaw of the light. Pity, because I don't think it would take too much extra thought to devise a more secure fastening system e.g. Velcro strap?

I've decided to keep the light on the bike to reduce wearing of strap (rather than put it on/take it off). Fortunately, the bike is never left alone to tempt the 'light fingered'

My friend has his just below the seat clamp on the frame on his cannondle EVO which works well. Obviously if you have a chunky frame this will not work

normally you can attach it just above or below your saddle pack.You definitely will be seen. It is designed for that part of the bike, could maybe work on a helmet but seatpost would be better as its too bright for a helmet. Hope that helps

Its got quite an adjustment on the strap. Used with a small saddlebag there isnt an issue. If you have a medium/large bag and your seat post extension isn't very long I'd advise getting something else.

YES

I can see your problem there, if your seat post is tall enough you may be able to mount it under a seat pack, it does seem it is designed primarily for seatpost mounting and won't easily adapt for other places.