I modified a MUJI 0.38mm pen that I had on hand pretty easily: just snipped off the bottom inch or so of the pen's refill to hold the Supernote refill. Took a pair of scissors and two minutes.

The MUJI pens retail for $1.50 if you have a physical store near you. Soft, polycarbonate body and lots of colours to choose from.

https://muji.ca/collections/pens-pencils/products/gel-ink-cap-type-pen-0-38mm

https://www.amazon.com/MUJI-0-38mm-Smooth-Ballpoint-pieces/dp/B07MSHFGZG/ref=sr_1_2