Here are two PDF documents, with square regions that have a triangular grid array on them. The grid is formed the same way that you would create one via precreasing, so it’s relatively similar to what you would see on a sheet of origami paper.
The first one has a very large grid; the second one has a fine, small grid. both are useful, just for different things.
These are newer versions, with the opacity of the grid lines turned down to only 20%; so hopefully if you draw on them with pencil or pen, your drawing will show up much more easily. The PDFs retain the layering and editing information, so if you also have a vector graphics program capable of editing such documents then feel free to tweak these to your heart’s content.