You can random craft every day and pray for luck, and ofc you can drop it with ultra low chance.
PS Sometimes you will see builds by cheaters, so no wonder why they use many rare items.
Boots are craftable, may take a few thousand scraps if you’re lucky.
For pants it depends, you should farm for witch gods pants in main campaign, for others like Kuba or Aleksander’s then Crucible is more efficient.
All those MI can be farmed in crucible, hoping for lucky drop. Just dont hopw for double-rare mod, a single rare and single magis is the best you can hope to get, and even then, it requires a lot of farming and good luck. Iems shown in that link, are realistically obtainable. I got Blighted Viloth’s Ring of Attack from Crucible recently for example, i bet it’s near-BiS for most acid builds… A shame i dont play any of those.
Getting 2 desired ultra-rare affixes (like Thunderstruck and of Kings) is highly improbable, even on non-MI base. You just want too much. Something like "resistant Greaves of Kings or Thunderstruck Greaves of Vitality can be crafted relatively easily, or dropped in Crucible too (i already got 2-3 of those).