Filtering & deleting comments based on specific text string

I run a blog at https://www.yousuckatcraigslist.com. For the last few days, my site has been inundated with spam comments that copy the entire text of a previous comment, and append the following text: “(to vote for this comment, please visit the site)” — minus the quotes. The comments all have URLs listed as a link from the “commenter’s” name, and the names are all common names like Sean, Kelly, and other normal sounding things. The email addresses are all things like “[email protected]” or “[email protected]”.

Is there a plugin or a way for me to filter comments to look for this string of text and automatically flag them as spam? I’m getting 10-15 of these per hour for the last few days, and the Akismet filter isn’t good at catching them because they’re existing comments that have already been approved.

I can’t use the WordPress moderation/blacklist options because it’s multiple words, and would flag everything containing ANY of the text “(to vote for this comment, please visit the site)”, which would be a lot of comments.

Ideally I’d like to filter the comments containing that string of text to the spam filter. Can anyone help?