Are there any good white and/or blue token generators?
If you accept planeswalkers as your tool to generate tokens multiple turns you may use one of these:


Dovin, Grand Arbiter as a Blue and White option
Karn, Scion of Urza as a Colorless option
Nahiri, the Lithomancer as a Mono White option
Ugin, the Ineffable as a Colorless option
Tezzeret, Artifice Master as a Mono Blue option


Now if you want creatures, these are the two best options I've got:


Mycologist as a Mono white option
Pallid Mycoderm also as a Mono White option