If it helps, sometimes you can find the source by grabbing the picture and reverse-searching it with Tineye.
For the sake of my mind, I'm going to use this and do math, rather than go further than the ten pages of google I went through looking for the weight of a yard of cloth-of-gold. A short sleeve shirt uses (usually) about 2 yards of fabric, so 1 yard of cloth-of-gold would weigh about 1.5kg. A cloak takes about 4 yards, as will the robes underneath, and lets throw in another yard for a belt, sash, or whatever. so 9 yards of cloth-of-gold at 1.5kg per yard would be 13.5kg, or ~30 pounds. If your guy is a big dude, tack on another 5-10 pounds, if they're a small bean take off 5-10 pounds.
he is a tol, but using the official kinging robes that already existed, so at least he doesn't have to deal with the extra ten pounds it'd weigh if it was long enough for him. :D thanks very much! yeah, he's not a weakling, he's fairly athletic for a nerd, but like... fencing and kung fu, not weight lifting. 30 pounds of shiny cloak would definitely be something he'd complain about having to wear every time he does any formal kinging.