Can anyone recommend a good one? Having a hard time finding one at all at any local gun shop, since it's a fairly new weapon.

What kind are you looking for? If strong side IWB two clipper hybrid style, I've become a huge fan of Black Arch Protos M holsters and they make one for the CSX. I just got one in for my new Bodyguard 2.0 in fact. They also make a one clip style version. After almost two decades of dozens of types and makers I've settled on hybrids as my favorites and BA makes fantastic ones. Can recommend if you are into that style as well.

https://blackarchholsters.com/collections/all/products/dual-clip-protos-m-2-0-for-smith-wesson-csx-3-1?_pos=2&_fid=e93677068&_ss=c

Will also add they make regular full kydex holsters and AIWB and OWB. Pretty much every style possible and pretty sure they have the CSX for all of them. Not sure if they have the new longer E series one though. Might just be the basic 3.1 in. I have not tried these other types personally but I have three of their Protos M dual clips (including a CSX one) and at this point I think I have found my forever holsters. I am sure their other offerings are good too though.

OWB clip holster.

https://upperhandholsters.com/products/owb-conceal-carry-holster?srsltid=AfmBOoq5NGRN4UpPs5XJ9R26HzB2SMUstpzDlbheWRoWNkmwzWotDiYi

Looks like they have holsters for multiple CSX variants. I have one of their IWB holsters with speed clips and I'm very pleased with it.

if you run a pistol light this is what you should get. i can use the same holster for my Staccatos and glocks as long as they have the same light.

https://www.phlsterholsters.com/floodlight-owb-range-and-competition-holster/

I use these guys for my IWB & I carry 100% of the time.

Its as close as you can get to a "custom" holster.

https://www.nsrtactical.com/

You generally don't find holsters worth a darn on the shelf of the local gun store, unfortunately. There are exceptions, but most gun stores carry crap.