I have a homemade vertical, here is a pic of the gas hookup.
(Blown up so you can see the gas fee thru the wall of the smoker)
The "bushing" is a 1 1/4 inch sink drain, it has a flat flange on the inside.
Here is a pic of the burner.
I designed this for easy cleaning/disassemble, so when I want to use electric, I just take the burner out and replace it with an electric element. The hole in the side that the gas tube runs through is large enough to run an electric cord through. I have that hooked up to a PID controller to control the temp, This is not necessary but is really convenient.
I found a "electric BBQ" at Wally world clearance for $20. Its 1500 watts and at that cost I may buy some as spares as they do burn out.
There is some posts around for a strip element that I really like as well.
The electric does not heat up as fast as the gas, but if you know it you can prepare for it. I have actually preheated my box up with gas and swapped in the element to save time.
I think on yours you could put an element inside and run the cord down by the burner.
Good to see you used Teflon tape on your connections.
Hope that helps, I will look for some pics of my burner and PID, I just cant seem to find them right now.