Instead of going for more "established" tubes like 6V6, 6L6 or EL84 it's possible to use odd types with similar characteristics. Buying them cheap as NOS saves a a dime or three. The 6AQ5 is similar to EL84 but has a slightly lower rated wattage.

Internet references:

I studied the Paraphase experiment for a long time and decided to go for it as it looked so simple, so I ordered the 6X8 from, brought a pair of Edcor XPP-10-8-8K from our trip to USA last autumn and ordered the rest of the components from Swedish company ELFA.

Mains transformer is from a butchered Heathkit amp and chassi was a Hammond steel, but became a slightly smaller steel chassi from unknown origin.