What kind of crankset are you currently running? It might be possible to convert it to 1×9, in which case you would only need to buy a chain ring. I did this with my 2×10, X0 crankset a few years back using a direct mount chainring from North Shore Billet.
You should be able to replace the big ring with a bash ring and the small ring with a 30t or 32t and be fairly good to go. I converted from 3×9 to 1×9 by putting a bash ring for the big rint and a 32t for the middle.. I am running a 12-36 cassette but I have ordered that 11-40 from Amazon.
I’m doing a conversion like this on my fat bike right now. If you want a little bit wider range check out this sunrace 11-40t 9 speed cassette. https://www.amazon.com/Sunrace-9-speed-cassette-11-40T-CSM990/dp/B01N95OJLQ/ref=pd_lpo_468_tr_img_3?_encoding=UTF8&refRID=YZMN5EDE1D1WKY37MQ72 I have mine on order right now. I’ll try to follow up once I get it on and let you know how it works.
If you have the money, and are willing to spend it, I would go 1×10 or 11. I have the 11 on my stumpy, and it is a great setup, you feel you have the same range, but it simplifies riding, and cleans up your bars a bit! Without the shifter.
So if you have the money, I would go with 1×10 or 11, or you could just get 1×9, will still work. The Shimano SLX/LX/Deore line is good, and can be found cheap, then you can strip one of the cogs off the crank to make it 1 instead of 2, that is a cost effective way to do it.