To be honest, most of my tubes came from ebay, but some came from vacuumtubes.net
For the rectifier, perhaps you can start off with the Mullard CV378, which is $120 at Well Audio at Burlington Square. If the U52 is electrically equivalent to the 5U4G, then the normal Tung Sol or RCA 5U4Gs can be a good starting alternative.
That's excellent advise. I am assuming $120 is in SGD? The GEC U52 is S$550! Ouch!
What about the power tubes? What good?