Change asset names in published content

Hi Guys

Bit of an unusual issue here: my client needs to host the storyline course via their website but for some odd reason their server automatically changes underscores to hypens in all content. As a result none of the png images in the project are displaying (because when published their names become codes with underscores in).

Is there a way I can stop this happening? Or change the asset names post publish to remove the underscores without breaking the content?I've asked the web guy to see if he can stop the underscores being auto changed to hypens on his side but we're not hopeful. 

Any help would be appreciated

Thanks

Harri