Im going to answer this both as a vendor and as someone who has or had to develop product that were similar to others (even with patent in place) in another line of work. This is an unfortunate aspect of free enterprise (like it or not) from a strickly business standpoint. Without IP protection it's really up for grabs. I had worries early on regarding one of my ideas and went the rather expensive and time consuming process of applying for a patent. I'm still in pending status but have protection on my side. Utility patents are the ones to have but a design patent can be easier to obtain. If Vendor Y has all his or her documentation and dates on his design a provisional patent can be applied for and that gives them 12 months to get it finalized. This does nothing for the short time but if Vendor X proceeds to produce an exact copy they run the risk of being taken to court when and if the patent is finalized. Vendor Y would have legal rights to all sales (profit) that Vendor X received from selling the copy and also possible lost sales. That is about all you can really do. It's sad but that is business. I risk it with anything I make or design. Now here is what we as consumers can do. Be educated about what we are buying. Do the research and support those that inovate. I can tell you that the consumers are smart and will notice this over time. Now vendor X has the freedom to do this but at minimum should either improve or offer a better solution. This is how innovation works. Even working around patents is a normal business practice. Straight up knock offs only offer short term gains and in the end tarnish the image of the company. Back to Vendor Y..... Now is when you should be working on the next better thing.
We have been around long enough now to have 2 of our products copied by other vendors in the MINI market, both times it was a short term gain for the company that stole our product idea, however over the years one of those companies has gone bankrupt and the other one is well on the way to going bankrupt. From my experience in the aftermarket world, when a company starts copying ideas, that means that they are getting desperate because they do not have the creativity or engineering experience to actually create their own products. For a company to simply copy another persons product without their permission shows the underlying low morals of the company also and any company that has that low of morals seems to eventually fail, at least in the aftermarket car business that I have experience with. If the company in question can not at least come up with a better version of it to sell, then they have no creativity or design sense and can only sustain themselves for so long on old ideas and knock-offs of other product before their business suffers. We look at the aftermarket business as a longterm game, some vendors look at it as a short game though and whatever makes them a quick dollar now is what they do. However, if you can not set yourself up to be around for a long time and be patient and treat people right, you will not be here longterm. So, it does suck if someone copies their idea, legally there is nothing that can probably be done, unless there is a design patent in place and there are funds to defend that patent, but longterm the vendor copying the design will suffer from my past experience.