Can't target be printed off the internet, and then just taken to a print shop and ask them to print up what you want?
if nothing else they can break something down into quarters ( 4 equal sizes, not 25 cent pieces
)... and then print each on an 11x 17 piece of paper....
then with plywood backing, put then together?
or if someone has a fancy printer at work or home that will print 11 x 17, then they can just do it at home...
just a thought... that would give you a target 44 x 68