I'm leaning toward an electric 3rd function, probably summits. They have one for a l39 and l47. Which one is closer to a l45? Does the pressure feed to it come off the loader PB port?
Hard to answer those questions with any certainty.
Yes, the pressure comes from the loader PB.
L39 uses the TL1000A loader same as your L45
L47 uses the TL1300 loader
The Summit kit is pretty much agnostic. Based on their skimpy pictures and description the main differences are the vakve nounting bracket and possibly length of the hoses.
Its not my money so I would go with the L39/TL1000A kit. The valve, joystick handle, wiring, boom hoses, and brackets should work fine. You may need to buy different supply side hoses or fittings.
Ask Summit for guidance.
Dan