This one has been sitting on eBay for quite a while. Appears to be unissued.
eBay also has quite a few aviation sextants. Some, like the A12 or AN5854 have eyeball averagers (you use your eyeball to average a number of pencil marks on a disk or pins on a carousel). I see 3 Kollsman sextants: an MA-1 (pendulous mirror), MA-2 (bubble), and a couple of periscopics. All 3 are with the clockwork averager. I cannot vouch for any of them – I’ve done various repairs to Kollsman sextants but some are beyond my abilities to fix.
If you see a listing by “mr.enfield” then look hard at getting it. He refurbishes aviation sextants and he will ship you a sextant in working order.