Welcome,
Ok, so that is a re branded MTD, I just went through the parts list and as usual these sort of parts can be a bit hard to find as the brake arm bolts up underneath the footrest. It is in fact pictured in the first breakdown, then refers you to the deck page where it is not pictured but is listed at the very end of the list. MTD part number 761-0169.
You may be lucky enough to find an mtd dealer still with one, otherwise you may have to look abroad. I did find in the Gripske book, part number CHD5396, which is a replacement for 761-0168, might be a little bit different but may be an option if you cant find the right one.
They are not critical, only there as a safety thing, most barely work anyway.
Deck belt is an MTD 754-0145 or a Gripske BEL6969