Yes they sell them. Unfortunately they don't sell them alone. You have to get the whole accessory kit.
https://www.audeze.com/isine-accessory-kit
I love the m300 because I enjoy them, with the comply tips, without eq. I'll add a little bass when desired, but they have adequate representation throughout. Don't know if you're Listening on phone, dap, or external DAC/amp, as that will all make a difference. I use a Dragonfly red paired with a JDS Labs C5 as a portable rig. It's fabulous. You shouldn't have any complaints, especially for the price. As far as Bluetooth mmcx the Mee electronics and the westone cables have AptX. I purchased the Mee electronics cable. Only "issue" is the curved cable used for Shure and the like Iem. I simply switched left and right, turned them inside down, and have the cable over my ear. I actually prefer it that way now. Takes a little more pressure off the ear because the cable is now running over the ear, so I actually use them that way in wired mode too