I can’t find details about this Polaroid 40” UHD tv anywhere, I can only find info about Polaroid 42 inch UHD TVs or Polaroid 40” 1080p sets. I’m not too bothered about getting a cheap set, I’ll play with the settings until it looks right. And my computers graphic card will be handling all the scaling.
https://www.bigw.com.au/product/polaroid-40-uhd-smart-androi…
Why do you want a cheap 4k TV?
A quality 1080p for the same price will still look better on somewhere between 90 and 100 percent of content (depending on what you use it for).
4k vs 1080p is still less important than other aspects of picture quality like colour, contrast, HDR, etc (and if you're not watching 4k content, as most people aren't, it doesn't matter at all).