Anyone know of a billet upper that is compatible with a DPMS lower?

SI Defense

Tried si's website but it's closed for another week.  Anyone know of a distributor for them or their asking price for a billet upper?

Are you referring to a dpms style or a dpms lower, also you mean larger chassis lr308 type stuff?  
This is from the industry forum, the debunking thread.
Our LR series lower receivers are machined from a solid billet of 6061-T6 aluminum, hard coat anodized per mil-spec and black Teflon coated.

Our LR series uppers are made from extruded 6066-T6 aluminum. There is also a 4140 steel upper available as an additional charge.
I believe that to mean that the upper is also machined from a solid piece of aluminum that is drawn to approximate shape and then machined.  The fit and finish on the lr stuff is much better than the 223 sized chassis.  Not sure exactly of the others available now that would match perfectly, there is a thread about the large chassis stuff interchangability in the ar10 section, but I do not know how current it is.  For my last 308 build I went with the smooth sided dpms upper and it is very thick nicely made.  I like the looks better than the forward assist/door style.  Especially with the chrome bolt in it.

POF, SI Defense, JD Machine, Kaiser, Iron Ridge Arms, JP, ADDAX (uses JD) and although it isn't out yet Tactical Machining is working on one.  I don't know which companies actually sell their uppers separately but as far as I recall thats all the DPMS lower compatible uppers that are billet on the market today.  

DPMS does make a leightweight upper that looks like a billet upper rather than the overly rounded side found on the traditional uppers by DPMS and Fulton

Hope that helps