Can you get some trimmed fat off another cut of beef and just lay it over the tri-tip? I've trimmed
out a bunch of tri-tips and have taken off as much as a 1/2" inch of fat cap before actually throwing the meat on the "q". Later, after grilling, I'd remove the rest of the fat.
You should be able to approximate this by simply topping the seasoned meat with a fat cap from another piece of beef. Good luck.
