Renfrew has posted the new molfile to params code:
This tarball contains more than you need; it has a pretty good README though. You can skip down to step 5 or 6 if you already have a good molfile of your adduct. (There are also a few notes specific to a different project – you should just ignore those).
This link will stay live for a few days, but won’t be good forever, so make yourself a local copy of it.