Does anyone know of a trading card sized template?

The sleeves for the standard trading cards out on the market can handle
cards that are 3.5 by 2.5 inches, although the two cards I measured (Harry
Potter and Pokemon) were shy of that by 1/16th of an inch on both edges,
probably for ease of sliding them in.

We were looking for a template to share in an online group, as we each are
making flash cards for a different segment of a common curriculum, and then
sharing the results. We wanted our results to be standardized, so that all
the flash cards when put together were a common size and format.