Findings:

• trs (user)
• TR
• Très Riches Heures
• T$R
• Tré Cool
• TRS
• tred (user)
• Erkki-Sven Tüür
• TRR
• tr (user)
• TR Spivey (user)

If you Log in you could create a ".tr" node. If you don't already have an account, you can register here.