Product Concept Ideation Sketches

I’m in the middle of a product design engineering assignment and have hit a wall during the ideation and concept-development phase. I already know the basic problem I’m trying to solve, but I need visually compelling concept sketches—quick, clear, and inventive—to move the project forward... (Budget: $30 - $250 AUD, Jobs: AutoCAD, CAD/CAM, Digital Art, Graphic Design, Illustration, Procreate, Product Design, Sketching)