Is there anything similar to motorbike roadbook holders for bicycles?
Personally I just use the map case on a handlebar bag (needs to be oriented properly to work), but here's a clever DIY solution by Raymond Parker:



Basically it's a piece of wire bent to prop the cue sheet at the right angle.  Put your sheet in a waterproof case or ziplock and a couple of binder clips hold it in place.  A shock cord keeps the whole assembly in place.  Full instructions here:  http://veloweb.ca/garagepages/sheetholder.html