Tuckahoe Gunworks and Hydrographics in Denton MD has done the engraving on two SBRs for me. An AR15 ($60) and a Z5-RS ($75). Turnaround time was about a week and he color filled the engraving. The MP5 cost slightly more because he didn't already have a jig setup for it.
He lists strange hours but if you call he'll likely be able to meet you at a different time. The shop is behind his house.