Client-side javascript protection

I'm looking for a way to block thieves or spy tools from accessing my URL. I already have a solution that performs server-side checks based on user agent, IP address etc. but these can easily be spoofed by the thieves. I'm now looking for client-side javascript that will help to better protect my URLs. Solutions that work on both desktop and mobile devices would be great, but that seems to be a challenge, so therefore I'm currently mostly looking for solutions that prevent the thieves from seeing my URLs when they are not on a real mobile device. If you do know of possible solutions that would work on both desktop and mobile, then I would be very interested in such solutions as well of course. The javascript code will be stored on the server-side. I already have one straightforward verification check build, so I will provide you that script so you can add additional checks into it. The end solution should be invisible to the regular end user i.e. there should be no popups (e.g. no popups that ask for geolocation). The better and more advanced the solution you come up with, the more I'm able to pay. Please reply with: 1. a high level description of the checks you are able to code 2. your price Thanks