That is pretty much the one I am thinking about as well. Found this from the same creator.
simMarket: TOPER CALCULATOR TOOL - B787 DREAMLINER (TAKEOFF PERFORMANCE CALCULATOR)
If you click “Read More” on the description, a special offer is revealed. Looks like you can buy 5 calculators for 6 Euro per app; or it says you get 5 calculators for 6 Euro. It isn’t clear to me. “Buy 5 for 6€ incl. VAT (6.00€ excl. VAT) each”