Hi Emilio,
Sometimes finding the right domain name can be a hard task. However, don't give up and just do some research and looking at other sites in the same field/niche, and that can give you some ideas as well. One thing that you can also do is look at a thesaurus website for other words with the same meaning of a name in the domain that you like, but is taken. As an example, if you are looking for a domain and wanted "FastTechSupport.com" but it's taken, you can look on a site like thesaurus.com and find other words that mean the same thing as words in the domain. Perhaps change "Fast" to "Speedy", "Prompt", etc.
You can also try some of the free domain name generator sites. Most are a complete joke and waste of time, but one that I have found useful at times is impossibility.org. It lets you use your words and will generate some domains that are available to register for you. It won't always give you exactly what you want, but it's also good for helping to inspire ideas that might lead to you coming up with one you like.
If you aren't looking for anything specific, you can also try 123finder.com. I have used it in the past but usually only looking for short available domains in certain extensions.
Good luck!