Hmmm. Dunno. Skinner's Horse wore pugris just like that for a bit (up to the mid 1890s), but they weren't lancers at that time. Caton Woodville could have made a mistake about that, I suppose, and painted a fellow in the new gear but with the old pugri and cummerbund.
There's also a Lovett plate of types with a fellow of the 5th Bombay Cavalry (Scinde Horse as was, and would be again) wearing one too, dating from the late 1880s. Don't think they'd have been lancers then though, either.
Sorry, that's all I got right now.