The KZ AZ09 Pro (and CCA BTX, etc.) have a charging case, it's not that big but will get the job done for some IEMs.

Otherwise wait for Black Friday sales or November 24, AliExpress and a lot of other sites will have the UTWS3 for like say $50 or less, I forgot now how much it was on November 11.11 sale.

If you want actual TWS earbuds that sound like the KZ ZSN Pro, unfortunately not a lot of TWS earbuds are graph on squig.link or Head-Fi, et cetera, and so few people can really know which IEMs will have a closer sound to it. Better to yes just get the TWS adapters like KZ AZ09 Pro and FiiO UTWS3 as it's pretty much as close as you're gonna get.

Here's a bit more info on TWS adapters like the FiiO UTWS3/5, KZ AZ09 Pro, et cetera, alongside adapters/converters, AptX Adaptive dongles, etc. needed for them: https://www.reddit.com/r/HeadphoneAdvice/comments/z1zklv/wireless_iem/ixdx9pt/ and https://www.reddit.com/r/headphones/comments/xjnapv/to_the_redditors_that_moved_from_tws_to_iem_were/ipa6qac/

Make sure you get the MMCX version of the UTWS3/5, here's more info about why: https://www.reddit.com/r/HeadphoneAdvice/comments/v3hs92/iems_help_need_a_new_pair/iaz200a/

Here's a more direct link for the adapters/converters required for the different IEMs and headphones: https://www.reddit.com/r/HeadphoneAdvice/comments/t3v7wp/looking_to_make_my_arias_wireless/hyv14dn/