There are two types of 2" webbing. One is harder because it is saturated w/resin to make it stiff. Conventional household machine even w/thick needle and even machine oil spray will fuzz the thread at the needle, most probably, mine did this. So for the small thing I rather do it manually. Walmart has a needle kit that has 6 needles for all the heavy duty hand sewing - sail, canvas, etc. ask the lady in the department. Also get a thimble. The whole square takes 10 minutes maximum to complete.
Special machines for this kinda job cost $700 refurbished on eBay.
Never seen brass rivets. Where would you get it? However stainless steel are available in HD and Lowes.
For the DIY sheath I actually preferred rivets because knife cuts the thread, even if mine is a blunt tip.