That's an SFX12V powersupply, not a standard ATX powersupply. So you'd need to replace it with another SFX12V powersupply.

Closest match to the one you have in the pic:
https://www.fsp-group.com.tw/index.php?do=proinfo&id=1766

Info on the SFX12V form factor:
https://www.formfactors.org/developer%5Cspecs%5CSFX12V_2_3dg.pdf

Here's a possible replacement powersupply from a quality brand. It might be too large for your DVR case, so measure first to be sure.
https://www.newegg.com/Product/Product.aspx?Item=N82E16817151063

Spec sheet doesn't list the noise level of the fan though:
https://www.seasonicusa.com/PDF/Catalog/NEW/Bulk/PC/SFX/SS-350SFE-Active-PFC.pdf