You don't have to use that type of compression fitting.
You can use a barbed fitting that accepts a softer tube.
Also, I think Autozone does carry a simlar tubing set as you have shown. Look near the gauges.
Boost Gauge fitting suggestion
You would need a "Barbed x Female pipe" for the back of the gauge. Probably this one:
Brass Double-Barbed Vacuum Tube Fitting Barbed X NPT Female for .17" Tube Id, 1/8" NPT