Options contracts are usually for 100 shares and the price of one share of Berkshire Hathaway Class A stock is $284,749. So one option contract would relate to $28 million worth of the stock. Most people who want to trade options on Berkshire Hathaway would buy options on the B shares. Why would someone want to buy options in the A shares and not the B shares?
Exchange listed options generally require an underlying security to be not only listed on an exchange but also have to have sufficient liquidity.
Many options exchanges will list an options class in a new stock if there is sufficient interest and there is a market maker willing to make markets in the options.
It may be possible to buy an option over-the-counter (i.e. not on an exchange) through an OTCDD (over the counter derivatives dealer) but these are generally where a large bank takes the other side of the transaction to meet a client's specific requirements and some commission.