If you make a basic garment as you are already doing, then turn it inside out and reduce the front by folding in half longways and pinning about an inch in the fold. Turn it rightside again and you will have reduced the front by about two inches, thus dragging the arms forward. Try it - it will be two tight. adjust the pins until you get a good fit. Once you have the right size you can stitch down the line of pins, remove them, and cut off the surplus fold of cloth.
The puppet book written by Waldo Lanchester and published by Dryad Press had a pattern for this type of costume. You can still get second hand copies.
There is at least one American, one French, and one German book which have a whole selection of patterns for glove puppet costumes. Why not contact Ray DaSilva. He will know.http://www.puppetbooks.co.uk