Well, I was going to say I've had luck with Canadian Tire bringing them in right around the end of build season... but that likely isn't going to help you much.
So maybe contact AndyMark
http://www.andymark.biz/bumper.html
And bring your bumpers as part of your withholding allowance.
Better yet... ship the bumpers as they are, find some pool noodles next week, then reassemble you bumpers at the competition if you have to (doesn't hurt to check the Q&A, but I suspect the answer will be "a pool noodle is a pool noddle"). A few pool noodles won't take up much of your 65 pound withholding allowance, and if you've got one or two students ready to rebuild the bumpers and the noodles cut to length you should be done fairly quickly on Thursday morning.
As for the "corners" bit... you can mitre the ends of the pool noodles (not the plywood) at 45 degrees, just as you would the corners of a picture frame.
Jason