Since Grant Fidelity dropped Psvane, hard to find reliable source. Never tried Viva as I've found their prices excessive. If they have good warranty service could be ok source. I've found Woo Audio a good source here in US, not sure they have that tube as they generally only sell the tube types used in their headphone amps.
One thing to keep in mind, you do not want Chinese stock to pick from, this means no Chinese sellers. Quality US sellers should have contacts at Chinese tube manufacturers to ensure they get best tubes off production line. China stock not good, don't care about reliability for their domestic market. I know this from experience, I'll never buy tubes from China dealer again.