It's going to be a pretty invisible laser display if you use a 5mW module - You'll need a dark and hazy room to see even the faintest whiff of beam, but the dot will be visible just about. The low-power blue diodes aren't avaliable at low cost since there is not demand for large-volume manufacturing unlike the powerful blues, which are used in quantity for things like some DLP projectors. You're just not going to find a super-cheap 445 diode like you can with some 532nm and 650nm lasers unfortunately, but they are avaliable at slightly increased cost.
I'm not sure personally how to reconcile a brighter display with safety - you would likely want to ask a member with more display experience on how it's traditionally done in this way.