g4560 cheapest cooler

The first and third links are for just a fan, without a heat sink, and you would definitely need a heat sink on there. The second link is for a very small heat sink that would probably only work with a very low-powered chip, and not a modern CPU.

The last link is closer to what you might be looking for, though they don't provide many specifics about the product. Does it include all the necessary mounting hardware for an 1151 motherboard? The listing is kind of vague about that, so it's difficult to say for sure. The same goes for how much heat it can dissipate, though I would suspect that the design is likely capable of adequately cooling a 54 watt CPU like the G4560.

Ideally, you would want to find a cooler that advertises compatibility with LGA 1151, 1150, 1155, or 1156 socket Intel CPUs (which should all be interchangeable), and includes images of any mounting hardware it might contain. Also, note that shipping from China and many places around there can be slow, although I'm not sure how it would be to Mauritius.

Another thing you might look for would be an Intel stock cooler for one of the sockets listed above. Many people replace the stock cooler with something else, and then sell the original. At least in the US, I can find some "new" stock Intel coolers on eBay for around $10 USD, though it would probably be more to get one where you are. Perhaps you could find one locally though.
 
To be fair, stock Intel coolers themselves aren't all that great, and I kind of doubt they cost Intel more than $5 to make. Intel has undoubtedly put a fair amount of research into getting the most cooling performance out of that minimal manufacturing cost though, so their stock cooler is likely better than most others in that price range.

I do suspect that there are better coolers than Intel's for under $20, but it's kind of hard to find reliable reviews on most lower-end coolers, since review sites tend to not cover them. Most likely that cooler won't perform as well as the stock Intel one, since it appears to have less metal in the fins, even if it has a larger fan. Of course, we are talking about cooling a CPU with fairly low power requirements here, so whether the cooling performance is better or worse than an Intel stock cooler might not even matter much.