This is a work in progress. Not all files are required
UPDATE 2022/01/21 - Foot file updated - adjust detente clip widths.
Split foot files removed - You can split the stand/foot in your slicer.

FileList

cisco_Spa500s-BRACKET.stl - This is joiner Bracket
cisco_Spa500s-Foot-full.stl - this is the foot/stand as a whole print.

Overall:

These are for mounting a Cisco Spa500 or SPA500S to a Cisco SPA540G IP phone.
I modeled these parts as I bought a sidecar attendant that had no accessories other than the thumbscrews.

Part1:

This is the joiner bracket. I designed this in tinker-cad with only a measuring caliper and pictures of the part. This is not a remix.

You can use a standard VESA mount M4 screw in the threaded inserts in the device.
M4x12 max. The printed example is using one OEM thumb screw and an M4x10 VESA screw.

Part2:

I am still working on the stand/foot part.
These are not completed yet. YMMV. I am working on 2nd version that uses the bracket holes for a 2nd unit. This should print faster but will prevent you from mounting a second attendant console.

Note: the foot is a remix of Cisco VOIP Phone Stand HH-M1-1. I clipped the detente points and squeezed the item to fit the needed with. I then shrank the detente points and re attached.
https://www.thingiverse.com/thing:3630300

Anycubic

All-metal Mega

No

No

25%

n/a

The OEM thumb screws have an un-threaded portion that can be used to keep it captive in the bracket. The bracket is 3mm thick and the screw holes are slightly under sized. You may want to ream the screw hole on the side with alignment pegs after printing. This will take advantage of the captive feature on the OEM thumb screws, and prevent the bracket from tightening with the threads.
If you don't have the OEM thumb screws, you may find it best to ream the screw hole on both ends to prevent the M4 screws from tightening against it .

The foot/stand is provided as a whole or in two split STL files. As I didn't want to wait 12 hours for the whole to print with a bunch of support material, i split it in half. Very little support material is needed. I used tree supports in Cura 4.12.1. this was only needed by the top half to support the detente wedges. The split files will need to be glued back together after printing. YMMV on the whole file, i have not attempted to print it yet.