The Lighthouse in Olivine City is a pretty good spot, if you skipped trainers in there.
Other than that, since the Kimono Girl's Eevee's are level 38, you should try to get your team at least to level 40. According to this guide, Seafoam Islands are a good place to train, alongside Route 47 (inside cave), Route 44, and the Ice Path.
Hope this helps!
