We've had a long and rough history with sandbags at the gym... Probably because we fill them with steel shot to 30lbs and throw them around occasionally. We found that we need to make our own now but the last sew-er we used didn't put enough reinforcement into the seams and a few have broken.

PKV can pay for materials and a bit for time but we need someone who can put a strong jean seam or similar through two layers of Cordura 800 as well as attach simple handles. Hand-stiching after filling them up works fine.