Hello,
I’m using the Gobe ND filters for my X7. They are very good and quite cheap. Available in 46 and 49 mm on amazon: https://www.amazon.fr/gp/product/B06XVC5T47/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
Laowa 9mm is just incredible!
Have fun!