TPU filament may be of use to your objective. It's very flexible right off the spool and usually requires a direct drive printer (genuine Prusa i3 - good choice) although I've printed with my bowden tube Sigma R16 with some effort. I won't try again, as it's far too much effort with a high failure rate, but on a Prusa MK2s, our local makerspace (library) has had quite good results. Slow speed is critical.

I've also printed flexible with OBC filament although it's a bit stiffer than TPU. At the very rigid end of the scale there's a product known as soft PLA, but it may be just flexible enough for your design.

If you'll be buying a printer this week, it's probably not a genuine Prusa, so much the sorrow, but be sure to get direct drive for the extruder.