Hey there. Generally UI designers charge much more for the entire set of UI graphics for games. Even logos tend to be over $50 on their own. For example, I generally charge $250 for the most basic UI, and increase my rates with the project's complexity. And that's just for the graphics, no programming included. I'm a GUI artist and may be able to give you a premade UI set for $15 but I can't think of anyone who has prices that might match your posted budget.
I will show you some examples of UI artists I have worked with, to give a concrete example of price ranges.
WinterMochie - Logo $45 | GUI $100 (starting price)
Camy - Small Noncommercial Bundle - $190 ($220 for commercial)
Sitraxis - Logo - $50-65 | Basic GUI Set - $200 | Extended GUI Set - $400
kathaeris - Logo - $80 | Standard GUI bundle - $250 (starting price) | Extended GUI bundle - $425 (starting price)
Also many artists have different licensing fees based on if a project is commercial or not, if any changes or alterations are made, etc.
Additionally, try to keep the forum rules specific to the Recruitment area in mind when posting in search of collaborators, it looks like your post might not meet the minimum requirements.
Recruiting Rules:
(1) Only recruit if you have an actual, clearly defined project you're recruiting for. Don't recruit if you're an organization that may have a project at some time in the future.
(2) Tell people what kind of work you have for them. For commissions, also tell them how much work it will probably be.
(3) Tell people how much work on your project is already complete.
I just want to give you a heads up so you aren't disappointed or surprised, but I also don't want to intimidate you too much. Good luck with your project!