The simplest way get a gradient background is to use a gradient backdrop.
This particular backdrop is made of paper, and is 80cm × 110cm (31" × 43"). Another backdrop at B&H Photo Video is PVC, 43" × 67" (110cm × 170cm). And yet another one at B&H is muslin, and is 5' × 7' if you need a very large product backdrop. Try searching Google, B&H Photo Video, Adorama, amongst others, for "graduated studio backdrop", you'll probably find what you're looking for.
Paper, coated paper, vinyl (PVC), and nylon polyester backdrops will probably have the most even coloration or color gradation. They can also be had in muslin (a lightweight cotton cloth), but as with most cloths, it will probably have slightly less even color consistency. See also the eBay buying guide, What Type of Background Materials Are Available for Photo Shoots?
You could also shoot against a solid white or chroma key background, and then create a gradient background in post. However, unless you spend a lot of time on the details to get it right, you can usually tell it was composited, rather than done in camera with an actual gradient background.