Choosing a microphone to build into an old radio

I’m planning to start using Picroft on a Pi4, built into an old-fashioned valve radio (I managed to find almost the model my family had when I was a kid!)
I’d like to use the radio’s own speaker (if it still works well enough) or a replacement installed in its place, with a DPDT relay so the Pi can switch it back to the radio (and then write a skill to turn the valve radio on, using relays, and turn its tuner using a motor). And I’d like the microphone to use the speaker grille, too (moving the speaker back into the case slightly if necessary.
The radio is one of these:
What would you recommend I use for the microphone(s)?

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Nice project!
Personally I would refrain from using the old speaker and tube circuits as there is a good chance of radio inteference with the RPI. And these old tubes might carry very high voltages, even after the device is switched off - you should be 100% sure how this stuff works and what you are doing there!

I doubt putting the microphone in front of the speaker will work - Mycroft won‘t hear you while music is playing.

Regarding mic choice you might want to look at
Maybe you can put the linear 4mic array in the top section of the front plate.

Isn’t listening while music is playing going to be a problem anyway?

The old speaker and tube circuits would be thoroughly isolated from the Pi, as I’d use a DPDT relay, so there’d be no connection between them. I probably wouldn’t use the radio very often in practice, it would be more that it would be a pity to make such a vintage thing unusable.

The linear array is probably a good way to do it; I don’t want extra holes in the front plate to be too obvious but if I can do them carefully (small drill and then needle files) I should be able to make them match the grille holes. What I had hoped for would be a 4 or 6 mic circular one with a hollow centre, and I had wondered about drilling lots of holes avoiding the tracks (just going through the ground plane) in one of the circular seeduino ones, so it would effectively become another grille, but I think that would be risking it a bit.