Tom Gardner wrote:

I can't seem to find loose 3mm balls, any ideas? I need to repack a linear
truck.

McMaster as always, search "bearing balls", catalog page 1124:

http://www.mcmaster.com

High-Precision Bearing Balls

E52100 Alloy Steel— Bearing-quality chrome-finished steel balls are
through-hardened. Rockwell hardness is C60-C67. Inch sizes conform to
ASTM A295.
Balls are Grade 25, with a diameter tolerance of ±0.0001" and a
sphericity of 0.000025" (unless noted).

E52100 Alloy Steel— Metric Sizes

Dia., Pkg.
mm Qty. Per Pkg.

3 100 9292K33 5.94