Well, you're gonna be hard pressed to find an alternative to chains, for their weight and even loading. Really you can hang anything from the barbell that'll progressively add weight as it comes off the floor, but chains are great due to the fact that they're relatively heavy for their size and provide a constant resistance change
Chains are far and away the most readily-available, lowest-cost system for what you're looking to accomplish if you're not going to use resistance bands.
stereolithography t1_j0gf0jp wrote
Curious as to why you'd avoid bands. They are one of the few simple things you can use to accomplish what you want and they're dirt cheap lol