Get some ECC83 JJ gold pins. Very reliable -- not expensive. Mullard NOS are not bad, RCA clear tops. Tesla 803c in place of 12AX7 are nice, but hit or miss as to what you can find.
Try here:
https://www.amplifiedparts.com/tech-articles/12ax7-comparison-current-made-tubes
Try here:
https://www.amplifiedparts.com/tech-articles/12ax7-comparison-current-made-tubes