GWatto said..In reality unless you are already heavily involved with an Olympic sport you have bugger all chance of winning a medal
90% of Olympians don't win a medal, so maybe set your sites to just become an Olympian.
Find a sport you where you can get to a standard to meet the Olympic qualifying standard, identify some long lost lineage from a country which has a particularly weak team or who are open to bribes.
Change nationality to said new country, pay said bribe, book in for your Olympic tattoo, simples

Perhaps clay target shooting, not as difficult as air rifles or archery because you have pattern of pellets and you only have to break the clay in two to have succeeded.
See you all in Brisbane
In case you thought I was being cynical or rude about clay target shooting, take up golf
Rory Sabbatini
Sabbatini was born in Durban, South Africa, and has Italian, Scottish and Irish ancestry.
In December 2018, Sabbatini became a citizen of Slovakia, the home country of his wife and stepson.[17] Sabbatini's wife's cousin is the vice president of the Slovak Golf Association. Initially, there was speculation that the move was made in order for Sabbatini to qualify for the 2020 Olympics, but he said it was to help grow the game in that country. The Olympics use the OWGR (Official World Golf Ranking) for qualification and the 201st-ranked Sabbatini would not have qualified for South Africa with ten others ahead of him.
One good round on Sunday and he got a Silver