Technical correction: It's not weed killer that one would use to make a bomb. It's fertilizer. Almost any fertilizer will work, although ammonium nitrate seems to be preferred by the nutcases.

I'll also sympathize and agree that banning saltpeter in quantities appropriate to salting a ham seems a bit over the top. It would take a fairly large amount to make a "useful" bomb, although one might make a few pretty impressive firecrackers with a cup of it.

It's been a very long time since I've encountered a genuinely nitrated ham. (The medical advice that the nitrate is bad for your innards has caused many people to use alternates.) The few I've run into recently who do their own all seem to use ordinary salt - sometimes insisting on "genuine sea salt" - often with a bit of ascorbic acid added to "sour" it a little. Perhaps an alternate recipe could be found; but you likely don't have time to try out new-fangled stuff between now and the holidays.

Legend holds that one can make their own. I don't recall that it included details of the recipe, but the DT may have the lyrics to "John Harrolson," "Von Hindenberg," or "Chamber Lye" where you might find reference to the DIY method, or check This Post.

John