Improving a product, who do I ask for help?

I have a plumbing-related product that is sold on Amazon, that looks visually pretty much the same as our competitors product. It has great reviews and functions very well for our customers.
I want to take the next step and refine it, to make a unique product with unique aesthetic and additional / improved function.
So, I need help with coming up with an interesting and pleasing visual design, that preserves or improves the current product’s effectiveness and durability.
I know I’ll need to hire someone for this. Is this something that is done with a product designer / industrial designer / mechanical engineer, or a different profession that I haven’t though about?

Link to the current product?

Sounds like you need an industrial designer. If there complicated mechanisms/moving parts that need to change, you may need a mechanical engineer as well.

An industrial designer should be able to help you creating a more visually impactful design. While you are investing in that work stream and new tooling an industrial designer can also help you improve the function. Ideally, to avoid commoditization, it helps if you are differentiated on three fronts: function, aesthetic, and brand. If you hire the right designer, they will be able to help on all three. I haven’t seen your product but I recommend considering function and brand in the same project so that the final product is differentiated, holistically thought through, and authentic.

Depending on your manufacturing partner’s capability and the complexity of the product you may also need a mechanical engineer and/or a sourcing developer to help get the new design ready for the factor and act as a day to day point of contact with the factory in the development process… These also might be the same person.