Hey there.
There are 3 options really. The first being have a lot of money (around $619,000 USD a share) and buy the Class A shares. Joking a bit here obviously as practically very few retail investors have this type of capital to allocate to a single equity.
Your better options are to go for the class B shares, BRK.B. You can do this on the US markets. Alternatively, if you want to keep currency in CAD, you can buy the Canadian Depository Receipt, which trades under a wide variety of tickers depending on your brokerage. BRK.NE, BRK.TO etc.
Just keep note that the CDR version will be currency hedged and as a result it does have a fee of max 0.6% annually. I typically do not own CDRs, I convert my CAD to USD and buy the US exchange options. However, everyone's situation is different and many people may find the CAD currency exposure to US stocks as a benefit.