I've been trying to find a new helmet recently using a specific set of criteria (carbon fibre, SHARP star rating, weight < 1.3kg, etc) but I've not been able to find a single site that allows you to search to this detail.
So I went and made one.
There's still plenty more to add to it (like feature search - drop-down sun visors etc) but so far it's helped me narrow my choices down considerably!
Currently only SHARP-star rated helmets are up there, but I'll be potentially look to add non-rated helmets as and when possible.
Hopefully the link will work for you all but if not, give it a few hours and come back (it sometimes takes a while for domains to become active across the world).
If you've got any comments or feedback then please let me know! Either use the link at the top of the page or reply here Hopefully it'll be a helpful tool for some of you! I know it's not going to be able to tell you exactly what helmet to buy, but it might help give you a short list so you can go into a shop and try those specific models instead of going in blind.