Check out upscaleaudio.com or thetubestore.com or Tubedepot.com for quality tubes. There are many brands such as Mazda,Siemens, Sylvania or even GE that can sound awesome. Have you tried 7189? Sometimes they have a "sweeter" sound and should be a direct replacement.
Keep in mind that some manufacturers make different versions too such as Amperex (globes) vs Amperex Trumpeter/Bugle Boys.
Keep in mind that some manufacturers make different versions too such as Amperex (globes) vs Amperex Trumpeter/Bugle Boys.