I have used this twice, but would rather pack with a jockstrap.
https://www.freetomprosthetics.com/collections/quarantine-sale/products/copy-of-gen-2-sleek-5-4-in-1
Selling for £125 originally bought for £200. I will post tracked, in a blank box, very discreet. Postage, as tracked will be £10. If I post to the US, it will be £20.