As said expensive if only doing one to buyt a suitable reduced shank bit.
Would only cost a few quid to get done at a engineering place, as they wil have this size or similar bits.
I use bits larger than this in the lathe, but these are 13 shakes reduced so would fit in a ordinary drill, I use blacksmiths drill bits up to 55mm.
If doing yourself just drill pilot dead centre(as best you can) then gradually open with sucessive larger drill bits to the max size you have ie 10mm or 13mm normally, then use rotary file or rasp to do last bit.
tabetha