That transistor "IMD3 T108" is a strange fellow. You can find info by Google it. Yaesu part # is G3070053. I'm sure they have it in stock. Can also be found elseware used by Panasonic and others.
Are you sure that the FET, 2SK2685ZT Q3004, isn't the problem? That is the UHF amp. Yaesu part # G3826857. Quite common easy to find.
Rgds
Nils SM7DVO
Nils Ostman