However, after thinking a few moments about your plight, I have made a change that should help you out.
If you set environment variable AFNI_ALLOW_ARBITRARY_FILENAMES to YES (e.g., in your .afnirc file, or somewhere else), then AFNI programs won't do the filename 'badness' check. If you do this, then you can create almost arbitrary filenames -- of course, you are responsible for dealing with any problems that result!
This change (and the MPEG change I mentioned in a previous post, for slowing down .mpg animations) is in the source code now, and will be compiled into the binaries sometime today.