Well, you didn't state which hotel you will be staying at, but if if is Non - Disney, that is your best bet.
Here are some other options:
http://www.viptoursandcharters.com/universal.html
Offers bus transportation for the following costs:
Adults 12 & up - $36 (transportation only)
Child 3 to 11 - $26 (transportation only)
Or, you can have the ticket price & tour included for :
Adults 12 & up - $67 (all day)
Child 3 to 11 - $54 (all day)
http://www.airportbus.com/apb6_002.htm
Also offers transfers, but this time on a shuttle, from any area hotel to Universal.
Adult: $20.00 Children (3-11) $15.00
The downside to these is that there are certain times you need to leave and return.
As per limos I'm sure that they would be willing to quote you one. Just do an internet search for anaheim limos or towncars, and I'm sure you'll come up with a ton of companies to try.
Sorry that I can't be more help
~Tina