judging by the fact of what you just said I would assume, You are being attached to a valuable person or persons of importance, whilst in the midst of the united states, "hence concealed to the average American, so as not to rouse suspicion"
I would first start with asking your employer, generally if they put you in harms way, they provide means of preventing that harm. If they do not you may want to reconsider your options. If you are wanting contract jobs I can point you in the right direction.
If your employer is not willing to provide with the means to conduct what is asked of you safely then consider what you will be doing, and what you will need. Read you Sit Rep and find out if the ability to prevent rifle rounds on just front and back is what you need, or if handgun round protection all around is what you need.
This will vary but im sure you already know all of this.
options for under plate carriers will be limited. most concealed vests are designed for trauma plates not ceramic military ones. The sets Ive dealt with are 8 pounds each and 6 sided in nature. These will not fit un-suggestively under a suit, or generic clothing. you will need to purchase slightly more expensive plates, if you do not want attention drawn towards you, and client.
for example: close quarters, indoor meeting with high end client. with expected total 60 seconds outdoors will not require under good circumstances a rifle plate."not saying it cant happen"
suggest purchasing PACA with highest level. worn one for years, never had issue. fits great and adjusts itself for entereing and exiting vehichles. plates however for this are very small.
Paca's products page is currently down or i would post links for you. If you would like more information or opinions
( I WOULD LIKE THE INFO VERY MUCH
)I would be happy to provide them to you. I understand your inability to not post details and will work around that for you.
Been there done this and that haha