3D Print CAD Design for Oblong Tube

I need a CAD design for a 4.5-inch oblong tube intended for 3D printing. One end should feature a 3/4-inch NPT thread for a standard pipe fitting, while the other end should be open and smooth.

Specifications:
- inside diameter 4.5"
- Length: 14 inches
- Shape: Oblong
- a funnel shape down to the 3/4 fitting
- End 1: 3/4-inch NPT threaded for standard pipe fitting
- End 2: Open and smooth
- Wall Thickness: Approximately 3/16 inch

Ideal skills and experience:
- Proficiency in CAD software
- Experience designing for 3D printing
- Knowledge of NPT threading and pipe fitting standards

Please provide samples of similar work.