Thank you for your interest. The vinyl I use is the same vinyl sold to sign shops for banners, car graphics, boats, signs, windows and much more. It will adhere to any smooth surface. I have had people use the vinyl on surfaces I never would have guessed it would adhere to but to this day they still are. It will adhere to the inflatable however I have never tried it so I could not tell you a good application method. The vinyl is very flexible and I am sure you would be happy with the results. Registration numbers are only $10 for the pair plus shipping which is only $3.00 first class mail or $5.00 for priority mail. My prices are very low compared to most of the sign shops locally. The benefit of a well known distributor and no over head costs with a home based business allows me to pass the savings on to you.
Even if you decide to go somewhere else, be careful because a lot of people are bringing in vinyl from china and it does not last more than 2 years. I use Oracal vinyl which is the top choice vinyl for the industry and has a rating of 5-7 years outdoors and unlimited life indoors. Thank you again for your interest. http://www.fgvinyl.com.
I was thinking of using a stencil and painting them on with vinyl paint, but at that price I think I'll give yours a try. Thanks.