You can find all of the appropriate part number for all your Seadoo parts if you lick on the "PARTS" link on the upper right hand corner of this page. Just enter your model's year and the graphic diagrams should aid in finding your specific part. I did a search for you and based on the fact that you have a 2000 Challenger, the part number is 204470139. But check it out yourself just to be sure. But to be sure, have a look at your MPEM - the part number is listed on the MPEM itself.
I changed mine out last year and I did the same thing - checked the part listing, but to be sure, I removed the MPEM and made shure it was the right part number. It is about 5 minutes work to remove the MPEM, but you may be able to see the part number without removing it.
Des