As the Praetorians are basiclly Mordians with pith helmets and are
expensive to buy plastics are a good option.
Wargames Factory is about to release a boxed set and the sprue is here
http://www.wargamesfactory.com/AnnouncementRetrieve.aspx?ID=16056
but the Martini-Henry rifles need a standard GW las gun end and
magazine added and they'll do a treat.
For metals you can go Black Treee
http://www.blacktreedesign.com/uk/product.php?
productid=25241&cat=2511&page=3
who also do gun crews.
Empress who have a growing range
http://www.empressminiatures.com/page2.htm

or Wargames Foundry
http://www.wargamesfoundry.com/collections/DA/index4.asp

So you'd have a nice force which looked the part, just add some GW bits
and pieces and you're away.