RParts has these unusual valves manufactured just for us.  We call them "Base Valves".  They are designed to stand upright and are bolted in place using a threaded bolt hole in the bottom.  They operate in the same way as a conventional service valve, providing three-way refrigerant access and shut-off.  We use them as part of our DIY kits to provide an easy way to isolate the compressor unit from the tube set and evaporator.