Skylight Diffuser

[quinciloo]

I have a tubular skylight in my bathroom. While pulling off the diffuser dome to clean it, it slipped, hit the floor and semi-shattered. Everywhere I've looked only carries an entire skylight kit. I have no idea of the model of the skylight. Checking online (and at retail places), I've found that most, if not all, diffusers tend to mount flush to the ceiling, whereas mine is more of a dome. Any ideas on what my chances are of locating a replacement and where to look? I would really hate to have to replace the entire skylight for a $10 plastic cover.