HDR is just a buzzword for TVs. For monitors, you have to actually look at the specifications to determine the number of colors supported and maximum brightness. High end monitors have supported 10-bit and even 12-bit color for a long time now and have different specified nits of brightness.
All 3 of my monitors are already 10-bit color, and many of them were made before HDR was a television feature:
HP ZR30w (Manufacturered July 2010)-- 10-bit color, 2K, 99% of Adobe RGB color gamut, 330 nits.
http://h20564.www2.hp.com/hpsc/doc/public/display?docId=emr_na-c02159509 If you look at the specs, this monitor currently has a higher color gamut than any television currently in production. Including the OLEDs. It doesn't get as bright as the brightest TVs, but IPS panels are darker than VA panels in general.
Dell UP3214Q (Manufacturered November 2013)-- 10-bit color, 4K, 99% of Adobe RGB color gamut, 350 nits.
http://accessories.ap.dell.com/sna/productdetail.aspx?c=au&cs=aubsd1&l=en&sku=210-ACBW Once again, this monitor is from 2013 and has a higher color gamut than any television currently in production. It's darker than the brightest HDR TVs, due to the IPS panel.
and my newest monitor...
Dell 2715K (Manufacturered December 2014)-- 12-bit color (downsamples to 10-bit), 5K (roughly twice the pixels of 4K), 99% of Adobe RGB color gamut, 350 nits.
http://accessories.us.dell.com/sna/productdetail.aspx?c=us&l=en&s=bsd&cs=04&sku=up275k3 At 5K resolution, this monitor is more advanced than TVs will be for probably the next 5 years. As a matter of fact, no single cable exists yet supporting 5K resolution, so this monitor requires 2 displayport cables. Once again, darker than brightest HDR TVs due to the IPS panel.
From my experience, the best PC monitors are IPS panels and darker than televisions' vertical alignment panels. That being said, these monitors are PLENTY bright and I have never thought they were too dark. As far as I know, no monitor manufacturer has used the "HDR" buzzword. Just get a monitor with the specifications you desire.
Note that only the highest end graphics cards can output 10-bit and 12-bit color. This includes AMD FirePro, NVIDIA Quadro, and the very high-end NVIDIA and AMD cards. My Titan X (Maxwell) can output 10-bit color, and I believe my 780 TI (Kepler) can also do it.