The Ka-Bar TDI is an excellent, low cost, defensive blade that benefits greatly from a quality sheath. The TDI LE Sheath from Kolbeson Leatherworks is the most recent TDI sheath option that I have come across. It is made from Kydex in the pancake style (2 pieces molded and riveted together) and has several eyelets for adjusting the ride height of the two included IWB soft loops. The soft loops are made from Brahma Webb Duroflex which is nylon webbing coated with PVC which is durable and has a leather-like appearance.
Check out the Kolbeson Leatherworks TDI LE Sheath.