For anyone interested in picking up the lens/diffuser panel themselves, it's 3/16" (NOT 3/8") square-based (NOT parallelogram/diamond-based) female (NOT male) conical (NOT pyramidal) prismatic diffuser/lens/panel/sheeting with the cells running in rows 45 degrees from the edges (NOT aligned straight across and perpendicular).
Plaskolite makes sheets of this in several materials: non-yellowing but breakable acrylic, virtually unbreakable but UV-susceptible polycarbonate, and the budget polystyrene material. In the acrylic variation, it's Plaskolite's OPTIX line, pattern 12, PL-21.
Here is Plaskolite's site for this style sheeting:
OPTIX Pattern 12 (PL-21) Prismatic Acrylic | Plaskolite
The polystyrene version of this panel may be durable enough to do several pulls, but I'm wondering if I should get the tougher acrylic.