For the standard itself I use 0.45mm brass rod obtainable from good model railroad shops. There are several suppliers on amazon (just search "0.45 brass rod") You need rod not wire as the rod is rigid. You will also need a VERY sharp scalpel and a pin drill with a 0.5 mm bit. You can get these as a dremel accessory with a thick shank thus increasing their survivability. Oh yes and of course super-glue.
At this stage you should mount the front rank of figures that will contain the standard bearer on its base and leave it to dry thoroughly first take the figure you aim to use as a standard bearer. If it's one of Walt's officer figures it's not a problem. If it's an infantry figure simply slice the pack from his back. Next with the scalpel make a vertical cut in the right arm in the direction of the body and cut to the body line. Now from the front of the figure cut vertically into the same arm along the body line until you meet the first cut and remove the slither of wood. You now have a recess in the body and right arm to sit the rod into. Now take the pin drill and 0.5mm drill bit and drill down the line of the recess and into the MDF web the figures are sitting on ie by the right leg. Now cut a piece of rod a little longer than you require and glue the end into the hole and to the recess in the figure. When it's dry, place a dab of super-glue roughly where the hand would be. This forms the hand when dry. Job done you have a standard bearer.
For cavalry figures it's much easier. simply drill a hole in the side of the figure beside the right foot. form the rod into an L shape and cut the short leg of the L just short of the body width.
Glue the short leg into the hole and at the same time glue the bottom of the standard to the side of the figure making sure it passes roughly where the right hand would be. again when dry form the right hand round the standard with a dot of superglue.
To make a finial is simple. simply squeeze the end of the rod with a pair of flat face pliers hence flattening the rod into a spear end shape if necessary trim it into a spear head with side cutters. Adding an eagle is not for the faint hearted. I cut the eagles from old Baccus figures and drilled a hole in the eagle base into which the rod can be glued. WARNING the eagles are very small and only marginally thicker than the drill bit. As I said not for the faint hearted!
I hope this helps
left:- nude command strip
right pack cut off to make an officer
left shows the figure with the recess cut. This can be done before or after mounting on the base
right drilling the hole in the web to take the base of the standard
the completed standard bearer. Only needs painting and the flag and finial added.