Navonics/Lowrance dowload question

[syd]

I just purchased the lowrance Elite 7 hdi unit. Really starting to love it.
Here is my question. It doesn't use the standard size sd card that i already had. It uses a smaller micro chip.
I was in the local Gander mountain this evening talking with sales rep about getting the card. He had recently purchased same unit and was not aware of that issue.
Anyway this techno type guy comes up and tells the both of us we don't need to go spend the $150.00 for the card.
He says we can go out and download it. All we need to do is go to Walmart and get the card.
If this is true would this be a Lowrance or Navonics site and what type card 8 or 16gb would work. The steps etc needed to do this.
Would love to hear back if anyone has done this.
As always thanks for your input.