You could try bottles of water. The 3 gallon square blue ones have molded in handles that would take a tie down or bungee cord. There are 6 gallon round versions that have handles molded in too.
Bella could easily run with a 6 gallon bottle of water tied to her neck, but I doubt she would run very far.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW