Oh, I was thinking the company was paying for it since it was work related
You can get any cheaper used graphics card off ebay, something with multiple monitor support like the K2000 or K2200 should be cheap ($40 - $90) and then get a cheaper version of the dock. The Powercolor equivalent of the Razer is around $240 (pre-COVID it was $175).
That should get you under $300 pretty easily.
Failing that, you could go with something like this: https://www.amazon.com/Lenovo-ThinkPad-Thunderbolt-40AN0135US-Capability/dp/B07M6S81CM
My main qualm with that is I’m unsure how good the 3D support of the multiple displays is. Passing through a real GPU to a real PCIe slot is one sure way to make sure there’s no jigery pokery going on with how the “GPU” is rendering on those displays.