NovexComm, as noted above are excellent but expensive.
For a few radios the ScannerMaster desktop racks are simple and effective. One guy here took a 4-radio rack and mounted a power supply on it to power the radios. He used a Stridsberg multicoupler for a self-contained unit, it was so sharp I copied it myself for my desk radios for a while. With these radio stands you could mount one radio on top and the rest below so a "4-radio" rack could actually hold 5.
For my main setup I have a couple dozen radios in a full size network cabinet, for less radios you could do the same thing with smaller cabinets. For scanners and 2-ways I too use the JottoDesk faceplates and the rack plates came from North Comm (
Radio Rack Mount - Fans & Radio Inserts). I have a bunch of the rack plates, a couple with built-in Astron power supplies. I have NovexCom custom racks for the big Icoms.
If you are good with building you can create a cabinet of your own, there was a guy here who build a great looking cabinet for about 10 radios by using a wood front with cutouts and brackets to hold the radios.
One of my possibilities at one time was to build (OK, have built...) a corner desk with a raised back for monitors that had space under the monitor stands for radios to be rack-mounted. That never got off the ground since I like to move things around and that would not work for that.