Hand-Spray Bidet Connection didn't work due to smaller existing pipes
Look for a compression fitting.in the plumbing department. Something like this as it's hard to guess the sizes by the picture.
https://www.homedepot.com/p/Everbilt-1-2-in-OD-Compression-x-3-8-in-MIP-Brass-Adapter-Fitting-800959/207176460?MERCH=REC-_-searchViewed-_-NA-_-207176460-_-N