I think it depends on how far you're willing to go for a silent keyboard.
The easiest, as Findecanor said, is to just buy an off-the-shelf keyboard with Silent reds/blacks. Don't need to do anything out of the box, but lubing them would improve it.
If you're willing to buy a more enthusiast board with hot-swap then you can also get Zilents and lube them but would be significantly more costly.
My preference for silent keyboards is actually silenced Topre. My silenced HHKB (Hypersphere) is the quietest keyboard I've ever used, but is now noisier because I've added other mods. A normal HHKB/RF with silence-X or deskey rings would also be very quiet. This would be a significant change from what you're currently using, though.
To make my keyboards quieter, I actually put a piece of foam inside the keyboard, like a neoprene piece or something similar. I also put a mat underneath to further dampen the noise.