Leo from beekeeb offers pre-build split keyboards like this one: https://shop.beekeeb.com/product/pre-soldered-wireless-dao-choc-ble-keyboard/ and it's within your 350$ range.
It should check all your boxes except a dongle and rgb. Regarding the travel case: He even offers a soft travel pouch in the store.
RGB on a wireless split keyboard needs a pretty big battery to have more battery life than a day or too, so it's difficult to find both rgb and wireless in a pre built one without raising the costs. Also some LEDs draw constant power without even being on which also adds to this issue.
ErgoMechKeyboards
Ergonomic, split and other weird keyboards
Rules
Keep it ergo
Posts must be of/about keyboards that have a clear delineation between the left and right halves of the keyboard, column stagger, or both. This includes one-handed (one half doesn't exist, what clearer delineation is that!?)
i.e. no regular non-split¹ row-stagger and no non-split¹ ortholinear²
¹ split meaning a separation of the halves, whether fixed in place or entirely separate, both are fine.
² ortholinear meaning keys layed out in a grid
No Spam
No excessive posting/"shilling" for commercial purposes. Vendors are permitted to promote their products/services but keep it to a minimum and use the [vendor] flair. Posts that appear to be marketing without being transparent about it will be removed.
No Buy/Sell/Trade
This subreddit is not a marketplace, please post on r/mechmarket or other relevant marketplace.
Some useful links
- EMK wiki
- Split keyboard compare tool
- Compare keycap profiles Looking for another set of keycaps - check this site to compare the different keycap profiles https://www.keycaps.info/
- Keymap database A database with all kinds of keymap layouts - some of them fits ergo keyboards - get inspired https://keymapdb.com/