You might have a try of green dot laser alignment. It can support 24 hours continuous dot projection. The green laser dot might be very large while working distance extends.
I have bought a 10mW green dot laser to make test at 25 meters, the green dot diameter is 8mm to 10mm. You can get more infor here: http://www.berlinlasers.com/532nm-green-dot-projecting-laser-alignment
Its output power is very stable, no dim of laser light. You might just have a try of this industrial laser pointer.
These people might have what you want. I don't have mine on me right now, so I'd be hard pressed to tell you the manufacturer. I went to green dot after working too many medical conferences. It's hard to see the red dot on an image of a surgery.