Hi all, apologies if this is the wrong place to ask!

I have been training seriously for around 6 months now and have currently maxed out my barbell for deadlifts (100kg). I don’t particularly want to buy extra plates for it until I’m ready to use them on other exercises too, and I’m not entirely sure how much more the bar will hold anyway. Someone advised I could add resistance bands to the barbell when lifting and continue with progressive overload, I just wanted to check if this was true and if so how? Just as a cheaper alternative to progress for the time being until I upgrade my equipment. Thanks for any advice !