These use heads and backpacks from Pig Iron. The heads are actually very similar to the ones pictured in the Codex under the Inquisitorial Storm Troopers.
As a unit, they cost a grand total of 60 points, including the grenade launcher. Being this dirt cheap means I'm happy for them to sit and hold an objective whilst my expensive Battle Sister squads go and do their thing. They won't take much punishment, but then again they don't cost much either.
For my Witch Hunters as a whole, I can probably stretched to 1550 points by tricking out every unit. Really I need to get another unit of Battle Sisters done but the only way that's going to happen is if I buy them in blisters or get them off ebay.