As evidenced by the many suggestions above, Imperials are abundant by borrowing from other 19th century ranges (the Eureka Chinese Pirates have some useful figures as well as the previously mentioned sources), but the Taipings are the problem, since queues and shaven foreheads are a no-no. You can get by to some extent with turbaned figures from some of these ranges (Old Glory have some boxers that work this way,) but you're likely to wind up with 'extras' that won't have any place in a Taiping force. I haven't gotten round to ordering any of the Wargames Atlantic figs (my Taiping Rebellion project is on a long-term pause) they're marketed as Boxer Rebellion but have separate queues so might be convertible with the right headgear.
It's a shame b/c the Taiping Rebellion is BY FAR the most interesting 19th century far eastern conflict.