Link external non-versioned resources to SVN repo

I'm using SVN for several projects that contain large binary files which are needed by the project but will never be modified (or they'll be modified on ve开发者_StackOverflow中文版ry rare occasions and I don't need to track their changes anyway).

As they're part of the project, I'd like to keep them "linked" to the project so that they would be retrieved when performing a checkout (or update if they're missing), along with all versioned files. But I don't need (and don't want) to have them versioned by SVN to save some space in the repo and avoid unwanted data duplication if someone modify/commit them by mistake.

Right now I'm using svn:externals on another repository (read-only), but something like svn:externals allowing links to non-SVN sources like an FTP folder would be even better.

Do you know any SVN trick or convenient tool that could help? Thanks!

Why not put them in the repository anyway, the benefits of having them 'linked' seems to outweigh the slight danger of someone modifying and re-committing them. I found this question relating to how good svn is at storing large binary files:

How good is Subversion at storing lots of binary files?