You can try http://www.synwin.com.sg/Scripts/default.asp which
sells things at fairly decent prices. The directions are in the
link.
As for a "violin maintenance kit", it's quite hard to specify.
Most violinists will not do much beyond cleaning their violins with
a cloth and changing strings. Anything more complex will be given
to a pro to deal with.
If you can find out your friend's brand of strings, or what
rosin they like, that might be more useful and practical.
Alternatively you can get them an expensive microfiber cleaning
cloth if they dont have one yet.
If your friend has been playing a long time, then they probably
have all that they require, so extra strings would be the best
lor.