90 volt battery eliminator

[tiv48]

hi i wounder if anyone has tried to use a nixi clock ht modul to get 90 volts for battery portables. im fed up of buying lots of pp3s , i attempted it once got 90 volt ok but so mutch hash nearly wiped out medeum wave,
or any other ideas to make these sets portable , idealy something that would fit inside original batteries
cheers rob t