I'll open with these :-
LED USB light
http://www.aliexpress.com/item/Flexible-LED-Bright-White-USB-Snake-Mini-Light-Lamp-For-Notebook-Laptop-PC-KH-06/591905228.html?currencyType=GBP&af=ppc&isdl=y&src=Google&albch=Google&aff_short_key=6vYvMRFf&gclid=CjwKEAjwhqShBRDS95LciqqaonISJADj1rgah9QMD3I1yKOEu0bSkHqCeW_RsSNhJvXMGn5oyPzIIRoC9wHw_wcB
Combined with a 3m USB extension lead and a mainsUSB phone charger it is really useful for seeing into the more hidden parts of the bike. Or you can wrap it around something to cast light where you need it.
Secondly this :-
Double sided tape
http://www.ebay.co.uk/itm/like/151033788182?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108&ff19=0
This stuff is so useful. Hangs number plates primarily but it's great for just about anything fairly lightweight. I've even used it to stick the PIR sensors for our house alarm to the walls rather than drill.