Dean Jones says:

"Certainly we can discuss a graduate assistant for you.  Of course, you realize that all of our grad assistants are paid a standard rate, so the budget for a graduate assistant is non-negotiable.  However, the duration of such an assistant is flexible.

Why do you want one?  And how long would you need one for?

Your response:

1.  I plan to conduct several big research projects, so ideally, I'd like a whole platoon of graduate assistants for four years at least!

2.  One or two would probably be sufficient...for two or three years.