Now is the buyer's market, you can start from two aspects:

First, find more suppliers and put some pressure on your current suppliers.

Second, according to the reason why they are dragging the goods, we should suit the remedy to the case. In fact, to do this job, we should not only handle the boss above, but more importantly, handle the personnel who directly handle affairs. As the saying goes, being strict is easy to deal with, and the kid is difficult to deal with.

I hope it works for you.