Acrylic would be expensive and relatively fragile for out side, a watering trough of poly would be cheaper, or like Mikestack said, a wood frame and a pond liner would work. It would also look good and could be painted or stained as you like it.
For a sturdy pond holding water 2' deep that has outside dimensions of 5'x8', approx 580 gallons you will need;
(2) 2x4 @ 8'
(1) 2x4 @ 10'
(5) 2x6 @ 10'
(9) 2x6 @ 8'
(2) 4x4 @ 8'
(1) pond liner sheet at least 10'x13'
(1 or 2) rolls of pond liner padding
and about 4 cubic feet of play sand
A little effort and some woodscrews with the above and you will have a very solid pond, you will still need a pump and filter though.