Looking for 4xPL 500 or PL504 valves.....please....i am desperate.

I really would be sooooo grateful if somebody can help me here.I received a gift of a Braun csv60 amp converted to a stereo power amp and i would really like to get some matching valves for her.Can anyone perhaps tell me what the approximate power output would be of this amp?She uses a pair of these per channel.
Cheers.