I had the same issue, and most of my shots are on off road locations with long walks, heavy stuff isn't an option, certainly not C stands.
So I bought a pack of these, any type will do;
https://www.amazon.co.uk …-19&keywords=bungee+cords
Most tripods have a hook for weighing it down or holding it down, I make sure any I buy do for this exact reason. So, I do this;
Dump your heavy bag under the tripod, bungee cord the tripod to the bag, sorted.
No heavy bag? Soft ground? Bring a plastic tent peg, weighs nothing and costs nothing, shove it in the ground, bungee to it, sorted.
Something heavy already there or a feature you can attach a bungee to? Sorted.
Pebbly beach? Bring a plastic bag, fill it with stones, bungee to it, sorted.
Cord too short, put two together, sorted.
Cord too long, double it over, sorted.
Object too big to clip to? Wrap some bungees around it, then attach a bungee from the tripod to the bungee loop, sorted.
Since I've put some bungees, a plastic bag and some plastic tent pegs in my tripod bag, which effectively cost and weigh nothing, I've not come across any situation since where I couldn't secure my tripod.