Just put in the message box what you want them to put as description, they can do it with e-packet and EMS :) Also, you can ask them for extra sealing of the content, and removing the box (just shipping the toy).

Come up with something stupidly uninteresting while staying credible: "aquarium decoration", or "zen candle", "dog toy", "pencil case"… (for onahole)

"birthday presents" isn't good, because it doesn't describe the content. That would raise suspicion ;)

If they still open it and ask you what it is… well.. I don't think they will understand the purpose, and you can then complain on how this "zen candle" looks shitty after all because it doesn't smell good and doesn't burn right and what a waste of money etc etc. Play the scammed buyer.

TL;DR
→ one item
→ e-packet shipping
→ no box
→ unrelated but plausible description

Wow, thanks for the tip man! I just realized how stupid the birthday present idea would be LOL Well, I'll try aquarium decoration or something of the sort. I'll come back and report how it goes once I received my package. Thanks once again and keep up the good work! Love the forum and the reviews, man! :D