It's been suggested before by someone with more imagination than me, but mk IV/1500 Spitfire bumpers look to be a possible source -
http://www.ebay.co.uk/itm/Triumph-Sp...3D162025345985
The fronts would need cutting down to quarter bumpers and capping off on the inner ends, while the back one will probably need a section adding to widen it enough to fit. You might just be able to use the discarded section from the front for that though. The whole lot could then be chrome plated for a relatively reasonable price (anyone any idea how much that should cost?)
The ones on Smash's car do look the biz, so it's well worth going the extra mile to add this detail if you can.