As
PlanetAlexander mentioned, light suits are a good way to go. Some 3d printed suits can be really heavy on their own (even when shelled out like yours) due to the infill or wall thickness used. In addition to tiring easy, heavier armor could cause more issues with strapping, as the straps would need to support more weight.
If you're going for a more flush fit against your body though, EVA foam is a good method. It can be glued and stacked in easily. For the areas where I did that on my armor, I placed the foam and test fit it with friction before gluing. I also used some of this softer, spongeier foam, which helped soften the weight of the armor while filing in the shells. 6 Pack Egg Crate Foam Charcoal 1 Inch x 12" W x12" L Acoustic Foam Panels Recording Studio Foam
https://a.co/d/4q9TrP8