I had similar issues finding a suitable shock for my Stumpy when my RP7 stuck down.  Spesh seem to spec custom length/stroke shocks which is why I had my old one serviced & PUSHed as it was way cheaper than buying an RP23 & having it 'adjusted' by Mojo.

There ar e minimal tolerances on the rear end (2mm on the Stumpy) which mean that the shock can foul the linkage or frame - especially if the stroke is wrong too.  I'm not sure if the original shock that came on it is adaptable by tft or mojo but a phone call will answer that - Tim @ tft will always give good advice & may have a 2nd hand shock he can reconfigure & revalve for you.  Might be your best bet too as they can set it up to match the wife's size, her bike & riding style - t'was a revelation when they did mine