I've got a 1x11 GRX setup on my gravel bike (40T chainring and 11-40 cassette) and it's lovely. Get the GRX derailleur and you can get a 40T or 42T from Csixx or Ali Racing works or the likes to work on your crank.
Then all that you are really paying for is: derailleur, chainring, chain, cassette and a cable)
That's my 2c
