Plate-mounted Cherry MX switches with nothing extra. The product code would be MX1A-11NN for Black, MX1A-L1NN for Red.
I suggest that you get a stiffer switch for the Space bar. A black Space bar switch for Red switches, or a A "Linear Grey" switch (MX1A-21NN) for a keyboard with otherwise Black switches.
Plate-mounted are nearly identical to PCB-mounted switches. If you get hold of some cheap PCB-mounted switch (say, from an old keyboard), then you could just snip off the extra plastic pins underneath and they would fit in the Phantom.
If you get hold of a switch with a jumper wire (four metal pins), then you would have to open the switch to remove it.
There are group orders of switches in the Marketplace here now and then. 7bit has a group order for MX switches on
Deskthority.
Be aware that group orders can take a long time - first collecting orders from members during a time and then doing the order from Cherry at once, then sorting and shipping each order, often all done by one person in his free time.