i think your best bet would be golden bell frogs if you have access to them where you come from
im currently breeding them for the same reason and if fed 2-3 times a day they can reach a max of aprox 5cm before they start growing legs and morphing into frogs.
theyre also rather easy to care for when i was younger i had aprox 15 of them i a tank and not long after there were a good 3-400 tadpoles in there aswell that i ended up just selling to a pet store az didnt hav room for all of them when they were tadpoles letalone after they mophed
and now am starting to breed them again , started a few weeks ago with 7 tadpoles fed 2 to my axie and left the others in the tank.
the bigest 1 just started growing front legs so will be a frog sune and im sure the others will sune follow
hope that helps