which IIRC takes you down to 500ft
You can set the VNAV profile to zero & 500 fpm and then make your GPS approach start somewhere "safe" and intercept the VNAV profile which theoretically will take you down to almost zero by the threshold (or wherever the GPS waypoint for the aerodrome is - probably mid field). Of course this is GPS altitude so going down to zero might be pushing your luck unless you have no other option.