Got me an Elite 113 inch (diagonal) tripod projection screen today for $181.00 CAD with free shipping from Amazon. I should get the screen between August 23-30. The talk is on September 2nd, so it should work out. I did not want to pay that much, but thought it might be better to go large so I could see what presentation looks like bigger, and it should also be more enjoyable for the viewers (hope hope!)
Here is the screen I purchased.
Here is the screen I purchased.