Is this really a DMR or a DPMS Rifle? BIG - BIG DIFFERENCE. Nevermind---I see you corrected.
I question in that the DMR is more like a high powered M1 Carbine 30 for Military(don't know types models they have), whereas the DPMS can be a AR15.
If it is the DPMS then look at WalMart for a CenterPoint 3-9 or 4-16. Bushnell has a 3-12(4-16) w/Illuminated also for $99. And there's a couple others. Nikon which is much better for around $149. You'll also need some Scope Rings depending on what Scope you choose.