You searched for "universal rectangular"
SPREADFAST
Heatsink, Universal Square Ceramic, 10.4 °C/W @ 100 lfm, 6.2 °C/W @ 400 lfm, 55 x 55 x 6mm, Adhesive, Screw
Part: SF-CHS-555506F
Ceramic heatsink for non-conductive cooling of sensitive electronic components.