I have seen a low cost switch that allows this, but then I spend most of my time on Cisco stuff. It is never low cost. I do not think there is an easy, low cost way to do this these days. The only thing I can think of is to read the manuals for a few low cost switches, such as those from Linksys and Netgear, to see if one supports port spanning or mirroring.

I just thought of a way to buy somewhat low cost Cisco equipment. You can buy it on eBay or from Horizon Data, Optimum Data, or one of the other companies that sell CCNA and CCNP practice equipment. These are older, used devices. Just be sure the one you buy supports port spanning as Cisco calls it. One other idea is Cisco FastHub 400. This is a real hub as I recall. One of these used Cisco device vendors may have one of these.