How to educate a font customer....

I got this plaintive e-mail from a confused font customer, and am trying to craft a diplomatically informative reply. Any ideas?

"I would very much like to use the font on a banner for my jewelry booth at a local market, but the largest size that My Fonts offers is 72 pt. Would it be possible to purchase larger sizes for my own limited use? And if not, what would be the best way to enlarge what I already have? "