Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4836358.
This is a remix of a remix. I really liked the 5-gallon bucket adapter by daemionfox (https://www.thingiverse.com/thing:4580194) for this modular hydroponics tower (https://www.thingiverse.com/thing:3405964/remixes), however, when I printed it in PETG, it didn't fit my 5 gallon home depot bucket (likely due to shrinkage and the design was already a tight fit). I ended up cracking it while trying to put it on.
So I used the original adapter file for the modular tower and incorporated all the principles I liked about daemionfox's adapter, however, I made it slightly bigger and one print (I have a 400x400 bed). I did change the fill hole to be a bit larger and made a simple cutout for the power cable. It does sit a bit loose on a 5 gallon, but I borrowed daemionfox's idea of putting holes to add screws to keep it in place. I've tested the weight and it was able to hold a 30lb kettlebell which is much more weight than the tower will be (assuming you don't go crazy tall).
To give this lots of strength, I printed it with 4 walls, and also used 4 layers for top and bottom in my shell settings. This is nearly a 30 hour print at 35mm/s, I didn't keep track of how much filament, but it is a fair amount so it will be a strong piece to hold your tower.
I have no idea how well this fits if you print in PLA.