You don't need to wait for baby expo to get things. Things in baby expo is not that cheap at all. The hassle of going there, looking for parking, squeeze with people and ppl mountain ppl sea.
For instance:
Buying diapers in bulk in lazada is cheaper. sometimes hypermarket offer the same deal.
In shah alam, there's a few stores that sells breast pumps, supplies and almost everything you need
You can find quiet a bit of things from shopee as well
Wait for some online baby fair, things are pretty cheap