Idling engines will often "load up" and stall when they've been idling for a while - although the fact that you've not got a LSN certainly isn't helping! If the engine seems well tuned otherwise then all you can really do is to bump up the idle slightly - as long as the clutch still isn't engaging at.

You are sure you've not got an LSN right? Sometimes they are located in the "barrel" and they don't look like an adjustment screw at all.

The only other thing i can suggest is that you blip the throttle when the car is stationary - this should allow it to idle for slightly longer.