Look at the suppliers shown here under Member Resources, under- Links. Then when you get one, look for adjustable powder measures. Try to find one that has a funnel attached at the top to make it easier to pour into your barrel. Rifle measures are adjustable, and are graduated by 5 grain markings, with readings every 10 grains, from 0 to 120 grains.I just checked Track of the Wolf, and it also sells a measure that adjusts from 40 grains to 200 grains, and sells the attachable funnel separately.
http://www.trackofthewolf.com/(S(t...ies/partList.aspx?catID=1&subID=13&styleID=49
Dixie Gun Works has one similar to the one I have been using for more than 30 years, although mine was made by Tingle.(No longer in business, to our loss.)
Expect to pay about $25.00 for a good measure.
I also have a measure with a pivot funnel on it, made by Treso. I don't like the pivot funnel, because powder residue gets into the pivot, and cruds it up. Either the screw loosens, which is annoying, or it gets to be work to pivot it open and closed.
I don't have those problems with my open top measure, with the funnel attached to the barrel, on a pivot arm that allows the funnel to stay out of the way, until I tip up the measure to dump the powder down the funnel.Some of the measures don't have 5 grain markings, but it doesn't take a Master's Degree in Mathmatics to figure out how to set the measure for 5 or even few grain increments in between the 10 grain lines. The measures are designed to through a comparable WEIGHT of powder using FFg powder. You will be close, in my experience, but usually not exact. If you are loading FFFg, throw a few test samples to determine what VOLUME marking you need to use to get as close to the WEIGHT of powder you desire.