I do not know if this is still happening, but back when I worked at Milan, Jerry Lozon was racing Jr's with his daughter, Jerry is now the Tech Director at Milan, back in the day Jerry would occasionally let kids who were interested in racing a JR make some passes with one of his extra cars, (a slow and very basic JR).
I do not know what agreement he had with the parents, but I know that it helped some parents out, some kids got into the Jr, and didnt want to race again, others wanted to race even more.
Again, I dont know if he is still doing this, BUT he is the tech guy at Milan and probably could make arraingments or get you in touch with someone that might be able to "rent" or lend or whatever you agree to.
PM me for his phone number if you want to talk to him.