Hi Brian, On the Aim-users web site there is an AIM spreadsheet that someone posted years ago and it's excellent--has all the machinery of classic AIM and more. I've tried AI and Newport but for most of my AIM I use this spreadsheet (with personal modifications). If you're at all facile with Excel this is a great route and it won't cost you anything.
It also allows you to see the values of the AIM parameters so you call see what's going on, whereas in software packages this is hidden.