Just looking for a safety measure to keep my pump safe if the line should plug for whatever reason (like ice).

I have searched a bit looking for a low pressure safety valve/pressure relief but there doesn't seem to be much out there. My system normally runs about 9 or 10 PSI with all diffusers on. A bit higher when I run just one for this winter so I added an extra line to act as a "bubbler" with no diffuser just stuck down in the water to let the pump run easier by bleeding a bit of pressure off.

What pressure setting would you buy and where can I find it? It would need 1/4 NPT for the easiest plumbing. Searches have turned up a couple but generally there isn't much in the low range that I have found and most have had mixed reviews on quality.

Thanks,
Dan