You can but RS 125 carbs from here in the UK
or Aprilia RS 125 inlet manifolds here in the UK
Aprilia RS 125 parts in the USA
So another easy job , none of the jobs on an RS 125 are really that hard but usually you have to take fairing off , take tank off , take carb out etc etc .
Anyway here is my photos of Replacing the 28mm Carb in a RS 125 it will be same process virtually fror the 34mm.
see other posts for tank removal .
so first remove air filter this is not standard so it come out of its hole
a lot easier
undo choke cable
and release cable from choke valve by push cable
end out of this hole
refit choke mechanism to avoid loss
Now undo 2 x 8mm bolts on carb lid
pull out carb float valve mechanism
again push cable out of its retaining holder and through its release hole
refit carb internals to avoid loss note how it came to pieces
Undo carb to inlet jubilee clamp
carb should pull free now without too much effort
undo all 5 allen headed inlet manifold bolts
You may need to pry the inlet out like i did as it was glued in place
if you needed to you can visually check your piston through the
reed valve entry .