Just FYI, when you’re looking for cheap cables (HDMI, VGA, USB, etc etc), I can’t say enough good things about Monoprice. I’ve gotten a bunch of stuff from them and it’s always been great.
They have a 50’ VGA cable for $13:
Their prices are almost unbelievable, but the products work. I have a 75’ HDMI cable from them that works great (and we’ll be using it at our VEX event in 2 weeks).
As for the rest of your list, can’t help much there other than to echo Rick Tyler’s comment about borrowing… every event I’ve been involved with has just borrowed monitors (even the World Championship), either personal ones for from work. If you can’t get your hands on a loaner for a weekend then I guess the next place I’d look would be on eBay or Craigslist or something for an old laptop or even a desktop PC. And there’s no requirement for an LCD either - a tube monitor could be placed on a short stand near a field and work fine. I’ve seen monitors like that being given away a lot lately.
As far as custom solutions, I’ve have 4 of these sitting on my workbench for a couple years:
My goal was to design a driver board with an XBee for wireless connection to a laptop for timing (though certainly a serial connection would work too), but I haven’t pursued it much further since it would probably be difficult to make such a timer for much less than $50. Also, it seemed to me to be getting easier every year to find laptops to borrow for field displays to the point where it wasn’t worth it, especially when you factor in that the field displays can provide other information that would not be available on a 7-segment timer.