Listed is a pair of Oneiric hockey base layer pants.
The company unfortunately went out of business, but they made some great under garments.
My son wore these at mini-mites when he was 6. Still in excellent condition.

This pair is size XX-Small and would be best suited for a mini-mite / mite under 7 years old.
It comes with built in shin guard pockets for easy on / off feature.

The Genesis Pant was designed for players who may be looking for additional protection on the back of the leg. Genesis' cut-resistant material around the ankle,, anti-bacterial fabric and more has got you covered.

BENEFITS

Cut-resistant material around ankle protects Achilles from cuts
Grip above knee secures goalie knee pads or shin pads
Secures socks with velcro on upper thigh
Mesh panels for optimized breathability
Includes a protective cup pocket
Anti-bacterial and quick-dry

MATERIALS

Anti-bacterial and moisture wicking for a cool feel.
Main: 72% Nylon, 14% Spandex, 14% Polyester.
Cut Resistant: 100% Polyethylene
Padding: 100% Polyester + PU foam
WASHABLE

Machine wash cold / Hang to dry / Do not iron or dry clean.