Find a generic part that behaves similarly. Need to simulate a specific Hall Effect sensor? Use a generic voltage source and a switch. Need a specific Op-Amp? Grab the nearest LM324; the gain will be close enough for concept testing.
Proteus allows you to create You draw the schematic symbol, assign the PCB footprint (from the extensive ARES footprint library), and if you want simulation, you write or attach a model. The "Missing Part" Crisis (And How to Fix It) Every Proteus user has experienced this: You download a datasheet for a cool new sensor, open Proteus to simulate it, search for it... and nothing appears. proteus library
If you don't care about simulation (you just want to build the board), find a component with the same pin count and pitch . Place a generic header or a generic IC, then manually change its PCB footprint to the specific one you need. Warning: Do this only if you know exactly which pin is which. Find a generic part that behaves similarly