How to get a cheap mechanical keyboard :
1) Go to Amazon or Aliexpress
2) Search "Mechanical Keyboard"
3) Sort by price
4) Check the reviews
I would suggest getting a 50-70$ cheap mechanical keyboard , cause those who cost less than 50$ are not that good and practical.
I would leave links/stuff to mechanical keyboards , but its not allowed to put links
Hope you find what you need.
My current keyboard (not mechanical but good af) - RedDragon Karura.