In terms of where to purchase replacement through axles you have a couple of options: you can connect with your local REI bike shop and have them order them for you or you can use an online axle specialty retailer like the Robert Axle Project.
Here are the specs:
Front: M15 x 1.5mm pitch, 125mm length with 16mm thread length.
Rear: 5mm thru axle skewer, 148mm functional length with rear spacing of 135mm.
Additionally, the dimensions of the thru axle on the front should be listed on the axle themselves when you remove them.
Hopefully this helps, thanks!
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