they sell U-tubes at various online aquaria retailers - U-Tube link
use a U tube bigger than your drain to avoid a restiction, so with a 1/2" drain, I'd recommend a 1" u-tube
when you go to bend the acrylic, just make sure it's plenty hot and you won't have any problems ... I originally bent the U in my overflow a bit too much, so I had to heat it up and bend it out a bit, no problems.
avoid getting the weld-on on any acrylic that is not a joint. the weld-on melts acrylic, and this melting can causes hair line cracks which are very bad.