You can edit the .ppd file for the printer and add in those extra trays..
a .ppd file is a Postscript Printer Definition file. It tells the print system all the information about your printer and it's features. where the margins are, the non-printable areas, the resolution, paper trays, duplexing etc..
I can't tell you specifically what you need to change but if you look through the file you may just find a few lines you need to uncomment to add support for those paper trays.
You can find more information on .ppd files on adobes website.. the wikipedia even has some links