I used a plastic storage box with a clip-on lid
I drilled several large holes in the bottom of the tender to let any water out and mounted the box on some 10mm blocks for the same reason.
I've had no problems at all, no leaks and it was cheaper than brass. There was also very little work involved in making the outlet and fitting it to the bottom of the box.
It's at the club but I can take some photos tomorrow.
Peter