Draw a sketch of it and take it into the tattoo place. Personally if I got asked to properly design a tattoo for someone (like shading/scale/etc), then I'd want paid for it.
You're paying for the artists time and skill, meaning you'll get a better quality product in the end. You're better going to an actual tattoo artist anyway, a regular artist could design something that is too intricate or complex whereas a tattoist will know what would work and what doesn't.
(Yes I realise this is a moot point coming from me but right now I don't think I'm at a level where people would actually commission me lmao)