Well, do you want to build it up by buying a upper here, a barrel there, and bolt/carrier assembly over here, or are you just wanting to get an entire kit?
I would suggest a kit of your choice from J&T or Del-Ton. They can be had with chrome-lining for about $500 you would also end up with an extra LPK if you went this route.
If it were me, I would buy a CMT 6 pos, stock for $70 (high side estimate), CMT flattop upper from Bravo Co. for $95 (or $99 w/M4 ramps), and a 16" barrel that is chrome-lined from various places for less than, say, $230ish, and a Bolt/carrier/charging handle assembly for $130ish (can be found cheaper, but I'm using high prices to set a ceiling for what you could pay).
That would put you in at about $530ish (probably lower with the right parts)
You could buy a complete RRA upper for just over $400 from ADCO that is chrome lined, but you'd still have to get a buttstock which would push you back up around $500.
Many options available, but if you decide to piece one together, you'll also have to buy $60-$70 in parts if you don't already have them.
Good luck,
WIZZO