I wish the LW was clearer about what she means by "young adult." Is her son under legal age (in which case he probably can't order himself a packer) or is he a legal adult who is still young? If the former, I get it and I sympathize with the kid. If the latter, I think he should buy himself his own damn packer (and if he can't afford it, ask for money for a Christmas present--he can tell his mom that it's for something private but important to him).

I am, for the record, a trans man myself; the mom's reaction doesn't come across to me as discomfort with her son's transness, just as, well, boundaries. Not everyone has the same comfort level. I don't think her reluctance to talk prosthetic penises with her kid is necessarily weird or invalid. As someone who is pretty seriously uncomfortable with anatomical discussions, I do actually have sympathy for her as well.