How about just buying an LED flood light bulb. I use R-20 LED bulbs. As my halogen bulbs burn out they get the R-20 LED. You should be able to get an LED bulb in any size. Amazon will have them. I realize you still have to deal with the height. How about using a 20 ft extension pole (common at Home Depot) and rubber bulb suction gizmo (again at Home Depot). Clear the area, put down a large tarp. Put on safety glasses and a hard hat (seriously) and see if you can unscrew the existing bulb. It might come free but then you have to close down the extension sections and that gets a bit dicey. The alternative is to rent scaffolding. I really don't think you need the retro kit as I understand, unless I am missing something about your description of what you currently have.
Not sure how tall you are and how comfortable you are on a ladder. I used one of these on my stairs standing on top. It was stable for me. I think the height I needed to clear was 17 feet and I was replacing a light fixture.
2015 Grand Caravan SXT Plus 5w-20 PPPP/Wix Filter 1997 Honda Civic CX 5w-30 PPPP/Mahle Filter
As my halogen bulbs burn out they get the R-20 LED.
It's just so hard to find them over 550 lumens without costing an arm & a leg.....
The lower watt ones are subsidized. How many times are you going to change this, once? Pay the $15. I'd test it in a lower-level fixture to make sure the color balance etc are what you like before the big climb.
I had to replace a fan with a chandelier 2 years ago - 20' up. I used scaffolding - 2 vertical sections. Yes a pain to setup, but imo, the safest. Get the safety railings as well. Glad I got them for my work. Use doubled heavy cardboard or plywood on cardboard to protect your floors. And get the wheels, easier to move around. They delivered to my home. $200 all in for the weekend.
2016 Sorento SX V6 AWD 2015 KIA RIO SX 2010 Mazda 3 2.0L 2009 Venza V6 AWD 2013 Sonata 2.4L RIP in write-off crash
I worked at a place that had a small electric vertical bucket lift. Just went straight up and down but would go well over 30'. It was on wheels and you just moved it where you wanted to go and take the ride.
Something like this. Don't know what the rental situation is around you.