While waiting for a place in Shichida, I bought a few sets from Flashcardsfactory.com at a book fair. 1-100 red dot cards, body parts & things to wear, alphabets
Once in Shichida, I bought most of its materials, which are sold to students only. And follow its system, which is much more than flashcards.
For instance, there's a specific method to use the 1-100 red dots cards to develop Lightning Rapid Calculation over 63 days. Just flashing the cards alone isn't enough.
I also make our own cards cos babies/toddlers absorb VERY fast. Got to change cards every 2-4 days, else they get bored and will not like flashcards anymore.
If you read Chinese, can get this book from library or bookstore:
BabyWorld.Com.Sg : 七田真0～6岁育儿法  - SGD8.05
My boy has been on Shichida classes and home practice for 1+ year and I'm happy with his progress.
Developmental Milestones of 25 months old toddler | Mummy's Reviews