If it’s a 6 speed then it ain’t a Rotax. I’m thinking you need to post a pic or two ’cause something ain’t adding up.
The double-calipers-on-one-disc was used for a bit, though I think it was gone by 2010. Might be a retrofit but the chassis might not be a 2010.
Matt, as far a parts go you’re best bet may be to deal with Italian Motors as they are Italkart. They have an online store and free shipping. http://www.italianmotorsusa.com If you can’t find it there, give them a call.
Fastect near Monterey also has a lot of Italkart stuff and Jon is super helpful