I have been looking around my local hardware stores & lumber yards and I can't find any places that have poplar. Where would I be able to find wood at and what would be the best size to start out with to make a trout swimbait? Thanks in advance.

Lowe's and Home Depot

There is a place here in nearby Toledo OH called Kenkraft, they sell their balsa and basswood to Janns, thats where i get my wood and its very reasonably priced!