Yeah, but it's not yellow.
If you really want to save money why not make your own?
I got hold of a 120 litre heavy duty plastic waste sack and cut it down to size, about a third off the top, leaving plenty to roll (like the Ortleibs). To hold the flap in place, use sticky-backed Velcro. Stick two strips of the hook side down one side two strips of the loop down the other (in line obviously). As you roll the bag up the hooks and loops fasten, so your bag is always the right size for what's in it.
Total cost: < £1
Sure it's not as tough, but at the price you can make up a few and take them with you, they take next to no space when empty.
Oh and they come in a range of colours. I got hold of medical waste bags and they're...
Happiness has 125 cc