Are you releasing your current MVC nuget packages to Octopus through a build server?
The other alternative is to use NuGet.exe which is a command line tool to create packages (Ocotopack is a wrapper around this).
If you're using something like TeamCity then this is wrapped up in the NuGet Pack runner - it just needs a path to the NuSpec file. If you're not using a build server then you may be able to run some post build command to fire up NuGet.exe. Here's the link to the command line reference for the Pack Command
Also, ensure that you've also got the usual NuSpec definition within your project too.