Try to restore from a 'saved' costume. Worse to worst, get a 'save' which uses the option. You'll have to redo the first two 'pages' i.e. your face/body style. Have fun
BTW if you are KDF, try enabling some of the unlocks, notably the ones from the 'adapted' set. Notice that the colour options are... 'uneven', as in the available options for say the 'left' accessory is no the same as for the 'right'? I suppose that's the result of KDF tailors using a bat'Leh instead of scissors for tailoring.
I got this recently on a character, no helmet, and no Honor Guard Beves uniform either. I loaded a saved uniform of one of my characters who had Mk XII honor guard set before s7 with the helmet and Beves and still didnt work.
So not sure when this was fixed, but I got my helmet last night!!!
Just tried a tailor, and found a helmet option finally!!
Would really liked to have seen this fix in some patch notes, but since I was so quick to complain before I wanted to put thanks where thanks was due now that my Mk XII Honor Guard helmet option is back!