Hi,
As people have suggested a VFD display would do the trick. Theres a couple of 200x64's on ebay (not 240x64) and some 122x32 going cheap. A 128x64 would be ideal though.
Again, an OLED would be nice as well, great contrast (2000:1?) and I know someone on ebay (US) that has a few going very cheap, I picked up a couple myself and they're easy to interface with a micro. Plus, they look the nuts
As for 'sources', Digikey and mouser carry OLED's and VFD's...altohugh the OSRAM OLED displays are pretty small (2.1" max). With all that said, PLED's/OLED's don't like direct sunlight much either, but they perform alot better than LCD's in that situation. There are extended temperature LCD's, which will work up to 70C, but thats ambient. The build up of heat in the display itself in sunlight would probably shorten its life a great deal. Have you considered making your own LED display? For segments, bargraphs, and shaped lightguides? Obviously not as purely configurable as a dot-matrix, but great readability and long life.
If you really want to go down the 'LCD' route, I'd suggest a few filters for the colour of your LCD, and some polarizers. They'll absorb a great deal of the light that isn't necessary for reading the display, before it gets to the LCD...and then theres always fans and coolers.
one simple idea, if you've got space, set up a couple of mirrors, so the display itself is embedded in the dash. Mirrors should scatter some of the light reflected back down the system, minimising the ammount shone on the LCD.
The last few idea's are a bit random, and probably not practical, but if you've got time, possibly worth a try. Very few forms of display can cope well in those conditions, with the exception of military grade displays.