Best proxy for draw price if goal scored?

Can anyone suggest a good method/source for estimating the price of the draw if a goal is scored 'now' (i.e. something that's based on other market prices)?

I'm interested in estimating a worst case scenario price, or somehow calculating the absolute lowest price, for the odds that will be available on the draw if either the lesser favourite (i.e. 1 < draw > 2, and 1 < 2) or underdog (i.e. 1 < draw < 2) scores first at the current point of the match.

I'm currently thinking that the price of 'Draw' in the lesser favourite/underdog Handicap +1 market might be good for this, at least if it's an early goal, but I'm not sure how time decay factors onto this / whether it would be better to swap the source after a certain point of the game / what other information might be useful in trying to form an estimate - so any suggestions welcome.

Thanks!