Bike mount for 4cm diameter large torch

[qazx]

i wanted to use a larger size torch on my bike, 4cm diameter, 15 cm long and about 500 grams.
has anyone come up with a mount that will take a large diameter torch?

ive got the twofish blocks but they only take a 3cm dia. light and are too wobbly anyway without further bungee cords.
thanks