You can cheat it in using the console or a savegame editor like
DaleKeeper.
To use the console, you must first enable it by adding the following line to icewind.ini under [Game Options]:
Cheats=1
Save and re-start the game. Bring up the console by pressing CRT+TAB. To put Marketh's badge into your inventory, enter the following at the console:
IWD only
CheatersDoProsper:CreateItem("marketh")
IWD:HoW
GETYOURCHEATON:CreateItem("marketh")