How to report sale of foreign stock in foreign FX for which I did not get a 1099-B from the non-US Broker? Translate to $ at the purchase and sale or only at sale date?

Sale proceeds = foreign FX rate on date of sale * foreign currency sale price * volume of shares
Cost = foreign FX rate on date of purchase * foreign currency purchase price * volume of shares

If reporting like this, because there is a FX loss, the gain will be much smaller than if I report the gain as (foreign currency sale price - foreign currency purchase price) * volume of shares * FX rate on the date of sale.

In essence, I would like to know please how to report capital gains from selling foreign stock in foreign currency, for which there was a FX loss (the foreign currency devalued against the $ over time).

I am an individual taxpayer, not a corporation. I use Turbo Tax Premier. Thank you.