If your needing some rapid prototype part for your project one company to check out is Proto Labs.

https://www.protolabs.com/

I saw adds for their company a few years ago for getting a design cube for free. it comes flat and when assembled its around 2″ on each side. It has molded in all the good / bad features to include with their processing. So if you want to use the company and these methods it can help guide your design before its finalized.

https://www.protolabs.com/resources/design-tips/design-stronger-molded-parts/