http://www.nasa.gov
JAXA (Japan)
http://global.jaxa.jp
Recommended Application on Smartphone about Outer Space:
NASA
Solar System Scope
NASA Be A Martian
ISS Live Now
Asteroid Alert
KIBO SCIENCE 360
Space Museum
Satellite Tracker
Space agencies such as JAXA & NASA has offered public to submit their name to be sent to space. There were successful launch such as Akatsuki, Curiosity, InSight, Perseverance, etc who carries people's name, messages & autograph.
Recently NASA make "Send My Name to Mars" program.
You can search on respective websites for more further info.
Try it yourself!
PS: I'm not endorsed by anyone.