If you search for slump bowl you’ll find plenty of topics were people placed acrylic over an inverted bowl, stuck it in an oven or gas grill, and let the acrylic sheet assume the form of the over turned bowl. Presumably you could try doing the same with a wedge to get your 90 degree bend. I don’t know how much stretch you’d get, but it may be worth a shot. You’ll find time and temperature discussions as well as a lot of debate about whether or not any outgassing of the acrylic is safe for your oven. Or you may just want to try a wedge and a heat gun. That way you won’t have to force a bend and snap it.
Here is an example of a slump bowl post: