I found a quick and easy way to magnetize the figures to the trays.
I found a magnet that has a hole in the middle that fits around the peg in the tray at Home Depot.
I found a 1/4" washer that fits on the figure.
I used superglue to hold the magnet and washer.
It does make the figures sit up about half the height of the base, but not too bad and with some good basing it should be relatively hidden.