Grommets can be a DIY job if you've got the proper tools.
Sewing new webbing on is a job for an industrial sewing machine at a canvas shop.
It depends on what's available to you and how much time / $ you want to spend.
Hiking strap material is not difficult to source - current stock width is 1.75" and I believe the material is polypropylene. Older tramps had nylon straps that were softer, but don't have the UV resistance of PP. Both are pretty cheap - less than $1 per foot - and you only need about 20 ft.
You can get either material in multiple colors from http://www.strapworks.com
Personally, I prefer sewn straps. Grommets hurt when you kneel on them. If you have the straps sewn, have them put a 1/2 twist in between attachment points. It keeps the strap raised a bit so you can stab your foot under it in a hurry.