I think it will be a struggle to find a purpose-made set of solo rules, or even a good set specifically for the SCW. So it's likely to be a case of adapting an existing set and making your own 'army lists' and what special rules you will require for them.
Bolt Action have an activation system that relies on the alternate drawing of dice from a bag to activate units, based on initiative rolls to determine which side has initiative. That could work well for solo play, as it allows action-reaction by individual units. I can't comment on how they play otherwise, other than to say I'm hearing good things.
Troops, Weapons and Tactics, or Through The Mud and The Blood, from Too Fat Lardies, both use a card activation system for leaders, which works well... and they also have supplements for the SCW. Good solid rules, but their use of 'blinds' is pointless when playing solo, unless you can make up some form of random deployment system using them, to give some of the 'fog of war' they represent in normal play.
All of the above are designed for 'larger skirmishes' (20+ figures a side) and feature all of the usual support rules (air, artillery etc) you are likely to need.