"tree" command output with "pure" (7-bit) ASCII output

The "tree" command uses nice box-drawing characters to show the tree but I want to use the output in a "code-page-neutral" context (I know that really there's always a code page, but by restricting it to the lower characters I hope to be free of worries that someone in Ulan Bator sees smiley faces, etc). For example instead of: ├── include │   ├── foo │   └── bar I'd like something like: +-- include | +-- foo | \-- bar but none of the "tree" switch combinations I tried gave this (seems more as if they take the box-drawing chars as the baseline and make it yet prettier) I also looked for box-drawing filters to perform such conversions without finding anything beyond an infinite amount of ASCII art :-). A generic filter smells like something to be cooked-up in 15 mins - plus two more incremental days stumbling into all the amusing corner cases :-)