Regrettably, under 15 U.S.C. Section 1125(c)(3)(A)(i), trademark law does not apply to: "advertising or promotion that permits consumers to compare goods or services." By using the phrase, "Gilbert style," the vendor falls within the above-referenced exception to U.S. trademark law.
Your recourse would be: (1) change your design to something that's unique and nonobvious, and obtain a trademark that you would imprint on your product(s); and a patent for the design; or (2) create some new unique and nonobvious (patentable) modification to the product that you can market as making your product superior to your competitors; (3) market your product as superior to your competitors, because yours is the original.
None of the above will provide you with immediate relief against your competitors, unless one or more of them decides to get rid of the "style" term in describing your product. If that occurs, then you can sue for infringement. However, in order to better protect yourself, you need to also register a trademark on your product name.
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