DMR makes a tensioner very similar to that Rennen one. My girlfriend has used one for years without complaint, although her riding is more commuting than dirt jumping.
Try the Singleator's "push up" mode before you buy anything new.
Has anyone ever used a chain tensioner made by Yess that mounts at the bottom bracket, like a freeride chain guide, and pushes the chain up toward the chainring? They look like they might be neat, although a pain to adjust.