The insulation is not required.
I ran mine for quite a while without.
When I switched to the K&N FIPK I wanted to seal the heat shield shroud to the hood. This requires the insulation.
The cowl section through the middle is open, so it is two separate pieces-
I used hood insulation retainers to attach them. Auveco part number 11130
The insulation that I used is a foil wrapped bubble sheet and is primarily a radiant heat barrier. It does deaden the sound some, but does not adhere to the metal to reduce the transfer of sound. It is available at hardware or building centers. I know HomeDepot and Lowe's carry it. It may come under different trade names. I have purchased Reflectix locally.
This might work as a good replacement for yours.