Best way to buy US shares now when I have £

Hi, hope this question is ok here…

I want to buy some shares listed on Nasdaq in $, but currently only have £ available in my account with my broker. The broker will exchange £ for $ (at a cost).

I’m debating whether to wait hoping the exchange rate will improve, at the risk of the US shares increasing in the meantime - is there any good place to refer to for predictions on forex? Or is there a good way I could exchange £ into another currency, then into $ for a better rate.

Thanks.

btw I am based in the uk