Angier,
I have a GX55 in my Archer. I got a used card with a current database off eBay for $50. A seller named merlinenterprise evidently has three subscriptions and sells single updates when he doesn't use them. You could also just buy a blank card, they sell for around $20. What you want is a 4MB _LINEAR_ flash card, not a regular flash card. There's a difference. These were use in a lot of Cisco network switches. I don't believe you will find the linear flash cards at Radio Shack.

Raymond Balister

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Sent from my Android phone with K-9 Mail. Please excuse my brevity.