Netscout has some EoL ones that are on the cheap these days.  These are cheap enough to forget at a customer’s site. 

https://www.ebay.com/sch/i.html?&_nkw=Netscout+280-0160

Netscout 280-0160

And yes a SPAN port on a switch is where I start sniffing. 

Kevin Burke
802-540-0979
Burlington Telecom
200 Church St, Burlington, VT

From: NANOG <nanog-bounces@nanog.org> On Behalf Of Dovid Bender
Sent: Monday, October 07, 2019 10:17 AM
To: NANOG <nanog@nanog.org>
Subject: Poor mans TAP

WARNING!! This message originated from an External Source. Please use proper judgment and caution when opening attachments, clicking links, or responding to this email.

Hi,

Funds at my 9-5 are limited. Has anyone tried this and how well does it work? We plan on mirroring about 800 megs of traffic at peak. https://www.amazon.com/Dualcomm-1000Base-T-Ethernet-Regeneration-Network/dp/B0055M5JL8?ref_=ast_bbp_dp

TIA.

Dovid