Are you looking for a donation or to buy one? 
I have a 20 dollar budget to spend,
but a donated one would be nice!
F.Y.I 11yr old I am.
To try for a donation, you should talk to your local schools and universities. If you have any electronics companies in the area, might be worth asking them as well.
Might also want to try and find a HAM radio group in your area if it exists, as they might be able to help (and possibly help mentor you a bit).
If you fall short on these, another member might be able to help, but it's more likely you'll have to find some odd jobs after school or during the summer to get something off of eBay. The linked eBay auction would run $30 if only one bid is placed for example, so there are inexpensive deals on decent, usable equipment to be had. Maybe even ask your parents to cover the balance and work it off in chores (just follow through with doing the labor without complaining if they agree to this

).