I'm exploring ways to discover available 2-3 letter .com domain names—are there specific tools or services that can assist with this search?
such as .net, .org, .info, or .io are also possible.

One of the key methods I employ is the use of domain name generator tools. These tools enable me to input specific keywords or letters and receive a list of available domain name suggestions that align with the desired criteria, including the desired domain extension. By leveraging these tools, I can explore a wide range of creative domain name options that may not have been immediately obvious, allowing for a comprehensive search process.

Furthermore, I frequently make use of domain name marketplaces and auction websites. These platforms offer extensive listings of available domain names, including short and impactful ones. By regularly monitoring these marketplaces and setting up alerts for specific keywords or desired lengths, I can stay informed about newly available domain names that match my criteria.

I also utilize the search functionality provided by domain name registrar websites. These registrars often offer advanced search filters that enable me to narrow down available domain names based on specific criteria, such as length and extension. This allows for a more targeted approach to finding suitable domain names.

Moreover, I conduct thorough research using WHOIS database search tools to gather information about domain ownership and availability. By analyzing the data obtained from WHOIS searches, I can identify potential leads for available domain names, including those that may be up for sale or nearing expiration. This approach allows me to uncover hidden opportunities within the domain landscape.

I actively engage in networking within the domain industry, leveraging social media and other online platforms to connect with domain owners who may be willing to sell or transfer their short domain names. Building relationships within the domain community can provide valuable insights and access to exclusive domain name opportunities that may not be publicly advertised.

Short domain names with 2-3 letters are completely taken, except for those that are not allowed.

As of a few years ago, a .com domain with just four letters was available. I'm not sure if it's still the case now.
If you're looking to find someone, you'll have to rely on symbolic representations only.