Oh, Google and I go way back. I own a couple of Mazdas too, but not an RX7.
You googled for a 5psi gauge but that is a 10psi gauge.
http://tinyurl.com/22tmzur
Don't know that I'd spend >$50 for a gauge that doesn't fit the bill much better than the readily-available 15psi model for half as much dinero (or less). I would drop that much if Don sold a 0-5psi gauge.