You could try the Weber WRVBPT with a bridge rectifier if you didn't have to have a 5y3.
260V 100 ma about 62 ma with a full wave bridge capacitive load, 6.3v 3 amp
I am using one for a low power PP 2 6v6 and get 333 B+ with. 2 12Ax7 1 12at7(reverb)
It is a stand up package.
In a SE Champ circuit I can't tell any difference from a tube rectifier.
I have and

the W022772 but 100 ma for a champ is 2+ x the power
the champ draws !