does anybody know if any online shops that has extra parts for the rally?
Depends on what you mean by "extra parts."
Since most of it is off the mini-slash, there should be a ton already out there at any online shop that carries traxxas. If it's Rally-specific, then nobody's going to have anything yet as it just barely came out.
Specific to the Rally I haven't seen any other than chop shop on eBay. Parts that are common with the Slash: yes.