Buckets (5 gallon or such) filled with water or sand. To the extreme, can mix quick drying cement in a bucket. That will form a much heavier weight. Some have formed BB plates with cement. Make a formed ring (lawn edging works well) with a PVC fitting in the middle (1 1/2 to 2") and fill with cement. Depending on the height of the edging, can make lighter or very heavy weight. If using a bucket, make sure it's heavy duty, with a good handle With water or sand filled, it's easy to add or reduce resistance.
Sandbags are excellent. Added bonus the grip and forearms become extra strong. Good for overhead pressing, any lateral exercise, rows, arms, etc. Rather than Kettlebells try the common sandbag for a different slant of working out. Cheaper.
Very productive exercises are chins & dips, if you want to go in that direction. Both mass producing exercises and you don't need any high cost equipment.Maybe only a bucket or cement plate tied around the waist. For curls & triceps, hold a towel on one end and have a bud hold the other end for resistance. Excellent exercise because the resistance can be adjusted during the actual exercise. From extra light to extra hard by your partner. Best preformed on a bench or mat.
As for vest, a backpack would be ready made for something like that, as long as you keep it high on the back at all times. Known guy's who have used truck innertubes (can be heavy), with some adjustments needed. Lots of exercises with truck tires, logs & cement blocks with handles. Good Luck.
