Have you checked the relevant best buy thread? Afaik, nobody is offering a 3-month fixed rate; you might be as well off just putting it in a variable rate deposit a/c if you can't lock it away for six months.
I had checked that thread and found a reference to a 6 month account but not for anything shorter. I know some of the banks etc were offering specials on 100 days/3 month accounts but a lot of these seem to have dried up.