I don't think you will find such an animal anymore. I think there was one or two made years ago similar to that but not resent (didn't Luxman and Krell make a big power class A). Pass Labs, Sungden, Accuphase and luxman are the manufacturers that come to mind that still make class A but nothing with that reserve power range. Really 50wch class A is about the max your going to find unless the amp also goes into class AB. Pure class A above that requires so much power dissipated as heat its not really practical nor comfortable unless you live in an igloo (ha that actually might be dangerous as the amp would melt the igloo most likely).
Hopefully someone else has a hidden class A gem they know of.
But in your nominal power output of 30-50wch pure class A your looking at Sungden. Luxman. Accuphase and Pass labs. few more but those are the biggest i'm thinking.
One more thing you may be surprised you may not need that reserve power if your speakers are a fairly easy load on the amp.
Love Class A SS but man they are space heaters. Tube amps are less hot go figure.....