Amazon has the ScanGauge II for $79.78 [amazon.com]
and is eligible for free prime shipping (shipped from / sold by Amazon). Must select Frustration Free Packaging option to get the $79.78 price. Lowest price ever according to a certain Amazon price tracker.
UPDATE: price is now $79.78. Was $91.91 earlier. It appears to be dropping every 12 hours or so.