Least expensive plug-in power conditioner that works

Furman PST-8 currently on sale from various vendors for $130.

I'm using one with the little computer mini-system rig and also (a week ago) added the iMac itself when our 20+ year old big APC unit conked out.

I'll pick up another one and dedicate it to the computer, modem and printer.

DeKay

I’d just get this that should be more than fine…

https://www.usaudiomart.com/details/650075208-audience-adeptresponse-ar1p/

Thanks for these suggestions.  
I was wondering about products like these;

QKOIL QK1 AC Enhancer

QVIBE Qv2 AC Enhancer

Puron Power Filter
ifi AC iPurifier

As compared to the Shunyata Venom Defender, or a less expensive power conditioning strip like the Furman.

The Audience does look promising.

kn

Fwiw, I run my modem and router into a PS Audio Power Center w- Virtual Dynamics Power 3 PC. It’s a well built and reliable piece of gear. Does it make a detectable difference?…mehh, can’t say for sure. Nevertheless I refuse to plug any component of my system into a $5- power strip.