The Beam crypto has only been available on the market for about a month, so there are not many exchanges where it is possible to buy Beam. it is a new high privacy cryptocurrency based on the MimbleWimble protocol, similar to Grin.
It is also traded significantly on the Chinese QBTC exchange, especially for CNY Tether, the Tether stablecoin anchored to the Chinese renminbi. On the same exchange it can also be purchased in bitcoin and USDT.
The third exchange for trading volumes is BitForex, where Beam can be purchased with bitcoin, ethereum and USDT.
Smaller trading volumes, and therefore reduced liquidity, are also found on Gate.io, ChainRift, Bisq and Codex.
In any case, the most common trading pairs are always with BTC, ETH, and USDT, while on QBTC it is also possible to buy Beam with CNYT.
It seems that there are no exchanges where it is possible to buy Beam with fiat currency, however, on Hotbit for example, it is possible to buy BTC with American dollars and then to use the BTC to buy Beam.
Be careful not to confuse the Beam cryptocurrency based on the MimbleWimble protocol, with the Beam token based on Ethereum: they are two completely different things that have nothing to do with each other. The Beam cryptocurrency is the one marked with the BEAM symbol and is already available on the market.