Bike shops will have spare axles . you need tools.. cone wrenches, 2 in order to take the axle out + a wrench on the
lock nut on the end,

Or Bring in the Wheel. the Shop Service Folks will do the work

the marketplace jumped over to freehubs to eliminate so many of the bent axles ,

Bearing races for axle were moved outboard, onto the end of the cassette..
but for the "bargain" end of the market. 6 speeds were functional, still are ..
A better tempered better quality steel, in the replacement axle may last longer,
than the OEM part, it, chosen for cost.

marketing sold 'more speeds' now the 8th speed is modest ,
the whole kit has to match the lever klicks so whole systems need to match.

so, then the parts list needed, you are quickly going to double the cost in the bike to catch up,

is it worth it ?, only you can answer that.