Hi,
I'm afraid there's no report PM button - unfortunately it's not currently an option in the forum software that we use.
If you look on the list of members online on the homepage, moderators are shown in a blue box - just forward the PM to one of those. You can forward it to me for now.
In future, the process we'll have is for members to forward any spam PMs to the Administrator inbox.
Cheers for now,
Darren