Sorry for the loss OP.
Maybe not what you want to hear right now, but I’m really glad Steam cloud minimises the impact of a loss. When I had a Nintendo Switch I was terrified of losing hundreds of hours of Dead Cells or Enter the Gungeon progress. Losing a Deck is obviously a financial loss (and the emotional attachment of someone special giving you yours), but at least there isn’t insult to add to the injury the way Nintendo would do.
For keyboards, 60% layouts can be bought prebuilt. If you want something smaller than that then you’re likely looking at DIY build territory or maybe a one handed gaming keyboard.
For a mouse, you can get really tiny portable mice that are low weight. If you want something that doesn’t tie you down to finding desk space, then you can look at trackball mice (fine for strategy games, not great for FPS).