There's a handful of ways you can go about doing this.
- Built in feature of Podio Item sharing, but as you've noted this is pretty cumbersome for the individual who is having those items shared with them.
- There is a pretty solid extension called Portal for Podio that will let let you do this: http://www.wau.co/Portal
- We also have built out customized workspace installation and sync between them as a completely custom solution. Typically the use case we implement these into is when our clients have 3rd party vendors that need to collaborate on the project, their clients who need access to the project to get updates, department workspaces, or even giving individual sales reps their own workspace so that they only get access to the leads they've been assigned.
If you have any questions feel free to reach out to me at firstname.lastname@example.org, and we can set up a conference call to do a screenshare.
All the best!