I'm assuming that since you specified "high intensity discharge" you are actually looking for a true HID light and not a look-alike for "show" purposes.
If thats the case there are a couple options for you. Deere makes a true HID light as as option on their larger machines, I'm pretty sure this could be adapted to your machine if you added some mounts on your ROPS better check with the dealer though. I think these lights require an external ballast box so there may be some issues with mounting that due to the space required.
A better option may be to use a light from HELLA such as the AS300 or 400 (Hella part # 996242501 12V) that has a built in ballast and is about the size of a standard work light mounted on your ROPS or perhaps fender.
http://cat.hella.com
CAT also makes HID work lights. Theres some good pics there of the difference between light output of halogen and HID too.
Caterpillar: Products>Parts>Operator Environment>Lights
True HID isn't just a coloured bulb as some think it makes a big difference, lots more light and a much longer service interval. Ive installed lots of them on off road equipment, especially woods equipment.
One last option would be to check what kind of bulbs are actually in your headlights (H4 etc) and check on Ebay. There are aftermarket conversion kits available for some types of headlights that may be useable in your factory ones.
Any of these options, except the last one, isn't going to be cheap though. HID is $$$, better count on at least $500-1000 per set.
Jason