5 gear replacement for 4 gear right shift availabel?

hi,
new to this enfield section here this may be a silly question:

After riding my enfield bullet (Indian) with 4speed gearbox for 27000 miles it neads som overhaul.

But before i would like to ask:

Is there a 5 speed gearset replacement availabel like the Quaife gearset for a nortnon?

I believe Hitchcocks sells one