I wear oticon spirit 3s too - i've had aids for 20 years now since i was 14, first in the ear, then bte as ite aren't powerful enough and the standard aids can now be programmed for my loss rather than needing to be specially made.
I've gone for black aids, magenta moulds, and I've added coloured metal rings round the tubing, making the whole thing look fantastic. And even with all that only about 1 person a year notices them without me mentioning it!
This is all on the NHS. High freq loss is the most common, but it depends on how severe your loss is. If it's 40/50 dB or more ites are unlikely to cut it, especially if you work with background noise, need the phone, etc.
I don't think ites are more discreet as you can see the bit in the ear easiest - the bit behind the ear and tubing no-onne notices. But as i said, people are dim and rarely notice at all.
Do you have problems at work etc with not hearing? After years of playing with aids and tech, the most useful thing by far has been boosting my confidence enough to insist people repeat themselves, write stuff down, etc. Other hard of hearing people say the same. Which means there's no point in my having 'discreet' aids.
I would be very wary of private sellers as they may not have all the expertise in tuning (not that the nhs always does, but at least each tweak is free) and many people find they've wasted money. other problem with ites is if they break you have to wait until new mould made so no aid for a couple weeks - with btes you can pick up a replacement same day.