Those wanting sand bags for beaver drowners can get them at ULINE.COM. I like the green 14x26" size. 39.00 for 100

Those work good, and I have re-used the bags several times at different locations.

Go down to your local tire place and see if you can find some large used inner tubes. Cut them Into 2 pieces so you have 2 segments. Then wire one end shut when you do that leave a loop In the wire so you can attach your trap chain or your drowning system.
Pre fill or fill at the trap site. Then wire the open end shut. If you don't pre fill you can attach your drowning system and the trap and just turn the tube Inside out and all your gear Is inside of the tube. Make for easy carrying. They will last forever. I call them the trappers condom.