SRAM AXS double to single
I haven't done it, but I am pretty sure it's doable without purchasing a new crank.
SRAM shows that switching between AXS 2x and 1x is as simple as changing the chainring: 
                
            
However, if you have AXS Wide 2x, it's 94mm BCD (vs. 107mm), so you will need both a new spider and a new chainring (AXS narrow-wide 1x chainring with 107 BCD).