The mug shot is 3.5 syns for a 68g sachet.
SW don't list syn values for Slimfast products - I think it kind of goes against the idea of their plan.
I don't know about a syn calculator though (except the estimator on the SW website)
It used to be that you could estimate the syns yourself by looking at the calories and counting 1 syn per 20 cals - but this only really applied to things that didn't have a free food in it as the first ingredient...
I've read that there is another method of fat content + carb content, then divide by 5.