Neutral form of "son of a <blank>"

I'm trying to come up with gender-neutral / androgynous forms of idiomatic phrases like "son of a gun", "son of a bitch", etc., substituting the "son" in each case for a neutral word that does not specify the gender of the person in question.

Alternatives I have considered: child, spawn, kid, offspring

None of them sound natural. Haven't been able to find much on this either on this site or the wider Internet, in the latter case possibly because there is simply so much noise from usage.

Although it's more than a little archaic, get of a <blank> doesn't immediately imply a gender. And it has the added advantage of being unambiguously insulting.

(Dictionary.com)

Noun 1. an offspring or the total of the offspring, especially of a male animal: the get of a stallion.

In fact, "get" by itself is still used as an insult in British slang,

3b. a child born out of wedlock.

abbreviated from whoreson get or get of a whore.

To me, "son of a gun" is already gender-neutral enough. I also find

I'm your man or I'm the man for the job

to be gender neutral.

I realize it might not be comfortable for everyone, but it works for some, and I wanted to make this option available to you.

Partial motivation for this approach: In Spanish, a man or a woman can be "un matemático" (a mathematician) or "un músico" (a musician).