Create a pager between fields I have a content type that has no limit on how many body fields it can have.

You can say that each body field represents a page in a book. You are supposed to switch page to see the next body field.

The client I am developing this site for needs to support visitors that have javascript disabled.

Is there a solution that makes it possible to add a pager for these fields using PHP?
If you can use Views, it'll be simple.

Views can provide each field's value as a row. Set it up to display fields, add your multivalue body field, filter by node id, and you can set up views pager to show one row per page.

Then, use Pathauto to create nice addresses for nodes of that type, like /multibody/[nid]. In views, use the same address and voila - node pages got overriden with your view. Use Global Redirect to redirect from /node/[nid] to /multibody/[nid] to make sure users will not end up reading whole node at once.