I did it, just bought a laptop HDD with the right size (physical dimensions, not storage size) and decent speed, swapped it over. IIRC it needed a bracket (straight off amazon) because the original disk was a different size, but it was ages ago. I followed a YouTube guide, but it was super simple.
I'd probably buy an SSD now, as you can get cheap ones and it may save a few seconds on big loads and boot, but it's a luxury, not a requirement.