Where can I find Steel and Ground types?

[V1ntage]

They only seem to be available in the underground network, but never encountered one, I'm struggling with the poison gym leader, any advice or other ways to get steel or ground types?

[Timber Dragon]

There's Klinks and Magnemites in Shade's gym, and those Magnemites can even carry Metal Coats needed to evolve Onix into Steelix (don't know what the drop rate is, though). I think those three are the only Steel-types available at that point in the game unless you picked Empoleon as your starter. Other Steel-types don't appear until you have full access to the Underground Railnet, after you beat Aya and the Yureyu Building.

Ground-types are risky with Aya since the field dampens their damage a bit and she has plenty of counters, like Tentacruel and some Ice- and Water-type moves. If you're dead-set on Ground-types, though, you have a few options:

-Phanpy in the grass next to Corey's gym (Bunnelby is there too but it's not that great...)

-Baltoy or Golett in the cave next to Corey's gym (need to bring an Ill-Fated Doll to the totem pole, and Baltoy or Golett will chosen at random)

-Trapinch if you have patience for Onyx Ward's arcade (I don't)

-Wooper and Palpitoad in Azurine Island

-Numel in Pyrous Mountain (not recommended due to 4x Water-type weakness, and Aya has Tentacruel and other Water-type attacks)

Might be a few others, but I forgot. In any case, you don't absolutely NEED a Ground- or Steel-type to take down Aya, especially with the counters she has and the field effect, but they could help.

[DW~]

Other ground types include Nidoking/Queen, which both get Earth Power (a ground move not nerfed by field) at 43 respectively, but be sure that the Nidorino/a has Hustle for SF Boost (Moon Stone is in slums) Psychic types are also useful, like Meowstic or Gothitelle (except for Drapion, but Nidoking/Queen or the rest of your squad can deal with that)