Congrats on your nice new DAC. I use this and it sounds so good I haven’t bothered to upgrade yet. At about 7 bucks it’s a way for you to assess i2S vs. SPDIF without risking a lot of $ (my cable is 6” long but now only available from 1 foot on up).
https://www.monoprice.com/product?p_id=24182
This one looks interesting to me and some people here have had positive comments I’d you’re up for spending $99.
https://wyred4sound.com/products/hdmi-pcocc-premium
This DH Labs cable also gets good comments and is a bit pricier.
https://silversonic.com/products/digital-cables/hdmi-2-1/
Just some potential options at a few price points to get started. If you’re looking for something more I’d look at Wireworld or Tubulus and think I read some good things about Wywires too. Regardless of the cable you want it as short as possible for i2S as it does not travel well and the signal degrades quickly over distance. Optimally you want 1 foot or less, but get the shortest length you can. Hope this helps, and best of luck.