They are fairly small, but there's enough room in the Deus coil for them.
For decades, the 'standard' in miniature relays has been the TO-5 packaged relays originally by Teledyne. Very expensive, usually used in Aerospace applications, and for very high frequency radio-signal switching. I've had the 'lid' off one in the past, they are works of art inside. My example was a magnetic-latching one, with two seperate coils for 'set' and 'reset'.
This is a typical version:
https://www.enrgtech.co.uk/buy/product/ET13974967/722-5