what do i wear to spray tanning app. when im under 18??

so the website to the place i’m going says that ppl under 18 must wear undergarments the whole time. this obvi makes a lot of sense but im getting one for the first time for my prom coming up, and i dont want a bathing suit chest tan line. would the best option be a cheap strapless bra i will wear once for this? any advice pls