Thanks, sadly those were not exactly popular over here that frontier engine. They didn't make them very long either iirc. Your best bet is to call some salvage yards here in the states like Al's Snowmobiles and what not. There used to be a link in the used parts area for that stuff. Also I would try at Polaris Star Forums as well. Link below! Good luck!
We are snowmobile enthusiasts supplying a community for you to ask tech and maintenance question on your Polaris snowmobiles. You can share your rides, sleds and even use the classifieds. There is no charge, completely free.polarisstarpower.com
Also can you do me a favor? Do you have the old one out sitting? If so take a few pictures of it and post them. Polaris didn't make those sensors usually they took them from another source and made them work. I know on the 500 EFI's some of them came from Nissan and so on. Same with the fuel filters as well. If you have some pictures maybe I can find some numbers on it or find another source for it other then Polaris.
Looks to be a Bosch Sensor possibly if you can find the Bosch number on it you should be able to get just that for much cheaper.
edit: Also give me the year and model of the Polaris this is going to. I can call a friend at a dealership and possibly at Polaris themselves if I can get hold of my friend there to see if they updated the numbers or have a solution no guarantees though