How to claim input tax credit while purchasing from e commerce sites like Amazon or Flipkart

Hi,
My query is how to claim input tax credit while purchasing from e commerce sites like Amazon or Flipkart ?
we will not have options to give our GST number So, if we claim input tax credit it will lead to mismatch as supplier will not have our gst number will filing his GSTR- 1 so that it will reflect in our GSTR-2A.